●

Asset Class Risk. The securities and other assets in the Underlying Index or in the Fund’s portfolio may underperform in comparison to financial markets generally, a particular financial market, another index, or other asset classes.

Prospectus [Line Items]

Risk [Text Block]

●

Cash or Cash Equivalents Risk. At any time, the Fund may have significant investments in cash or cash equivalents. When a substantial portion of a portfolio is held in cash or cash equivalents, there is the risk that the value of the cash account, including interest, will not keep pace with inflation, thus reducing purchasing power over time. Additionally, in rising markets, holding cash or cash equivalents may adversely affect the Fund’s performance and the Fund may not achieve its investment objectives.

Prospectus [Line Items]

Risk [Text Block]

●

Credit Risk. The value of your investment in the Fund may change in response to changes in the credit ratings of the portfolio securities held by Underlying Funds. Generally, investment risk and price volatility increase as a security’s credit rating declines. The financial condition of an issuer of a fixed income security held an Underlying Fund may cause it to default or become unable to pay interest or principal due on the security.

Prospectus [Line Items]

Risk [Text Block]

●

ETF Risk. The Fund is an ETF, and, as a result of an ETF's structure, it is exposed to the following risks:

●

Authorized Participants, Market Makers and Liquidity Providers Concentration Risk. Only an authorized participant (“AP”) may engage in creation or redemption transactions directly with the Fund. The Fund has a limited number of financial institutions that are institutional investors and may act as APs. In addition, there may be a limited number of market makers and/or liquidity providers in the marketplace. To the extent either of the following events occur, there may be significantly diminished trading in Fund Shares, Fund Shares may trade at a material discount to net asset value (“NAV”), and Fund Shares may possibly face delisting: (i) APs exit the business or otherwise become unable to process creation and/or redemption orders and no other APs step forward to perform these services, or (ii) market makers and/or liquidity providers exit the business or significantly reduce their business activities and no other entities step forward to perform their functions. These events, among others, may lead to Fund Shares trading at a premium or discount to NAV. Thus, you may pay more (or less) than the NAV when you buy Shares of the Fund in the secondary market, and you may receive less (or more) than NAV when you sell those Shares in the secondary market. A diminished market for an ETF's shares substantially increases the risk that a shareholder may pay considerably more or receive significantly less than the underlying value of the ETF shares bought or sold. In periods of market volatility, APs, market makers and/or liquidity providers may be less willing to transact in Fund Shares.

●

Secondary Market Trading Risk. Although Shares are intended to be listed on a national securities exchange, Nasdaq, Inc. (the “Exchange”), and may be traded on U.S. exchanges other than the Exchange, there can be no assurance that an active or liquid trading market for them will develop or be maintained. In addition, trading in Shares on the Exchange may be halted. During periods of market stress, there may be times when the market price of Shares is more than the NAV intra-day (premium) or less than the NAV intra-day (discount). This risk is heightened in times of market volatility or periods of steep market declines.

●

Shares May Trade at Prices Other Than NAV Risk. As with all ETFs, Shares may be bought and sold in the secondary market at market prices. Shares trade on a stock exchange at prices at, above, or below the Fund’s most recent NAV. The Fund’s NAV is calculated at the end of each business day and fluctuates with changes in the market value of the Fund’s holdings. The trading price of the Shares fluctuates continuously throughout trading hours on the exchange, based on both the relative market supply of, and demand for, the Shares and the underlying value of the Fund’s portfolio holdings. As a result, the trading prices of the Shares may deviate from the Fund’s NAV. Although it is expected that the market price of Shares will approximate the Fund’s NAV, there may be times when the market price of Shares is more than the NAV intra-day (premium) or less than the NAV intra-day (discount). This risk is heightened in times of market volatility or periods of steep market declines. Any of these factors, among others, may lead to the Shares trading at a premium or discount to NAV.

Prospectus [Line Items]

Risk [Text Block]

●

Geographic Risk. A natural disaster could occur in a geographic region in which the Fund or an Underlying Fund invests, which could adversely affect the economy or the business operations of companies in the specific geographic region, causing an adverse impact on the Fund and/or Underlying Fund’s investments in, or which are exposed to, the affected region. Also, current military conflicts in various geographic regions, including those in Europe and the Middle East, can lead to, and have led to, economic and market disruptions, which may not be limited to the geographic region in which the conflict is occurring. Such conflicts can also result, and have resulted in some cases, in sanctions being levied by the United States, the European Union and/or other countries against countries or other actors involved in the conflict. In addition, such conflicts and related sanctions can adversely affect regional and global energy, commodities, financial and other markets and thus could affect the value of the Fund’s investments and/or the investments of the Underlying Funds. The extent and duration of any military conflict, related sanctions and resulting economic and market disruptions are impossible to predict, but could be substantial.

Prospectus [Line Items]

Risk [Text Block]

●

High Yield Securities Risk. Securities that are rated below investment-grade (commonly referred to as “junk bonds,” including those bonds rated lower than “BBB-” by S&P or “Baa3” by Moody’s), or are unrated, may be deemed speculative and may be more volatile than higher rated securities of similar maturity with respect to the issuer’s continuing ability to meet principal and interest payments. High-yield debt securities’ total return and yield may generally be expected to fluctuate more than the total return and yield of investment-grade debt securities. A real or perceived economic downturn or an increase in market interest rates could cause a decline in the value of high-yield debt securities, result in increased redemptions and/or result in increased portfolio turnover, which could result in a decline in the NAV of the Fund, reduce liquidity for certain investments and/or increase costs. High-yield debt securities are often thinly traded and can be more difficult to sell and value accurately than investment-grade debt securities because there may be no established secondary market. Investments in high-yield debt securities by Underlying Funds could increase liquidity risk for the Fund. In addition, the market for high-yield debt securities held by Underlying Funds could experience sudden and sharp volatility, which is generally associated more with investments in stocks.

Prospectus [Line Items]

Risk [Text Block]

●

Index-Related Risk. There is no guarantee that the Fund’s investment results will have a high degree of correlation to those of the Underlying Index or that the Fund will achieve its investment objective. Market disruptions and regulatory restrictions could have an adverse effect on the Fund’s ability to adjust its exposure to the required levels in order to track the Underlying Index. The Index Provider may rely on various sources of information to assess the criteria of components of the Underlying Index, including information that may be based on assumptions and estimates. Neither the Fund nor the Adviser can offer assurances that the Index Provider’s methodology or sources of information will provide an accurate assessment of included components. Errors in index data, index computations or the construction of the Underlying Index in accordance with its methodology may occur from time to time and may not be identified and corrected by the Index Provider for a period of time or at all, which may have an adverse impact on the Fund and its shareholders. Unusual market conditions or other unforeseen circumstances (such as natural disasters, political unrest or war) may impact the Index Provider or a third-party provider and may cause the Index Provider to postpone a scheduled rebalance, which could cause the Underlying Index to vary from its normal or expected composition.

Prospectus [Line Items]

Risk [Text Block]

●

Inflation Risk. Under certain market conditions, the Fund may invest in an Underlying Fund that is subject to inflation risk. Inflation risk is the risk that the value of assets or income from investments will be less in the future as inflation decreases the value of money. As inflation increases, the present value of the Fund’s assets may decline.

Prospectus [Line Items]

Risk [Text Block]

●

Issuer Risk. The performance of the Fund depends on the performance of individual securities or other assets to which the Fund has exposure through its holding of Underlying Funds. The value of securities or other assets may decline, or perform differently from the market as a whole, due to changes in the financial condition or credit rating of the issuer or counterparty.

Prospectus [Line Items]

Risk [Text Block]

●

Liquidity Risk. Certain securities held by an Underlying Fund may be difficult (or impossible) to sell at the time and at the price the Adviser would like. As a result, an Underlying Fund may have to hold these securities longer than it would like and may forego other investment opportunities. There is the possibility that an Underlying Fund may lose money or be prevented from realizing capital gains if it cannot sell a security at a particular time and price.

Prospectus [Line Items]

Risk [Text Block]

●

Market Risk. The Fund’s investments are subject to changes in general economic conditions, general market fluctuations and the risks inherent in investments in securities markets. Investment markets can be volatile, and prices of investments can change substantially due to various factors, including, but not limited to, economic growth or recession, changes in interest rates, inflation, changes in the actual or perceived creditworthiness of issuers and general market liquidity. The Fund is subject to the risk that geopolitical events will disrupt securities markets and adversely affect global economies and markets. The Fund’s NAV and market price may fluctuate significantly in response to these and other factors including economic, political, or financial events, public health crises (such as epidemics or pandemics), or other disruptive events (whether real, expected or perceived) in the U.S. and global markets. The Fund could lose money over short periods due to short-term market movements and over longer periods during more prolonged market downturns. As a result, an investor could lose money over short or long periods of time.

Prospectus [Line Items]

Risk [Text Block]

●

New Fund Risk. The Fund is a newly organized, management investment company with a limited operating history. In addition, there can be no assurance that the Fund will grow to, or maintain, an economically viable size, in which case the Board of Directors (the “Board”) of The RBB Fund, Inc. (the “Company”) may determine to liquidate the Fund.

Prospectus [Line Items]

Risk [Text Block]

●

Operational Risk. The Fund is exposed to operational risks arising from a number of factors, including, but not limited to, human error, processing and communication errors, errors of the Fund’s service providers, counterparties, or other third parties, failed or inadequate processes and technology or systems failures. The Fund and the Adviser seek to reduce these operational risks through controls and procedures. However, these measures do not address every possible risk and may be inadequate to address significant operational risks.

Prospectus [Line Items]

Risk [Text Block]

●

Premium/Discount Risk. The market price of the Fund’s Shares will generally fluctuate in accordance with changes in the Fund’s NAV as well as the relative supply of and demand for Shares on the exchange. The Adviser cannot predict whether Shares will trade below, at, or above their NAV because the Shares trade on the exchange at market prices and not at NAV. Price differences may be due, in large part, to the fact that supply and demand forces at work in the secondary trading market for Shares will be closely related, but not identical, to the same forces influencing the prices of the holdings of the Fund trading individually or in the aggregate at any point in time. However, given that Shares can only be purchased and redeemed in Creation Units, and only to and from broker-dealers and large institutional investors that have entered into participation agreements (unlike shares of closed-end funds, which frequently trade at appreciable discounts from, and sometimes at premiums to, their NAV), the Adviser believes that large discounts or premiums to the NAV of Shares should not be sustained. During stressed market conditions, the market for the Fund’s Shares may become less liquid in response to deteriorating liquidity in the market for the Fund’s underlying holdings, which could in turn lead to differences between the market price of the Fund’s Shares and their NAV and the bid/ask spread on the Fund’s Shares may widen.

Prospectus [Line Items]

Risk [Text Block]

●

Reinvestment Risk. Reinvestment risk is the risk that income from the Fund's portfolio will decline if and when the Fund reinvests the proceeds from the disposition of its portfolio securities at market interest rates that are below the portfolio's current earnings rate. A decline in income could negatively affect the market price of the Shares.

Prospectus [Line Items]

Risk [Text Block]

●

Risk of Investing in the United States. Certain changes in the United States economy, such as when the economy weakens or when its financial markets decline, may have an adverse effect on the securities to which the Fund has exposure.

Prospectus [Line Items]

Risk [Text Block]

●

Securities Lending Risk. The Fund may engage in securities lending (i.e., lend portfolio securities to institutions, such as certain broker-dealers). Securities lending involves the risk that the Fund may lose money because the borrower of the loaned securities fails to return the securities in a timely manner or at all. The Fund could also lose money in the event of a decline in the value of collateral provided for loaned securities or a decline in the value of any investments made with cash collateral. These events could also trigger adverse tax consequences for the Fund. The Fund could also experience a loss or delay in the recovery of its securities if the borrowing institution breaches its agreement with the Fund.

Prospectus [Line Items]

Risk [Text Block]

●

Tracking Error Risk. The Fund may be subject to tracking error, which is the divergence of the Fund’s performance from that of the Underlying Index. Tracking error may occur because of differences between the securities and other instruments held in the Fund’s portfolio and those included in the Underlying Index, pricing differences, transaction costs incurred by the Fund, the Fund’s holding of uninvested cash, differences in timing of the accrual of or the valuation of distributions, the requirements to maintain RIC tax treatment, portfolio transactions carried out to minimize the distribution of capital gains to shareholders, acceptance of custom baskets, changes to the Underlying Index or the costs to the Fund of complying with various new or existing regulatory requirements. This risk may be heightened during times of increased market volatility or other unusual market conditions. Tracking error also may result because the Fund incurs fees and expenses, while the Underlying Index does not.

Prospectus [Line Items]

Risk [Text Block]

●

Valuation Risk. The prices provided by the Fund’s pricing services or independent dealers or the fair value determinations made by the valuation committee of the Adviser may be different from the prices used by other funds or from the prices at which securities are actually bought and sold. The prices of certain securities provided by pricing services may be subject to frequent and significant change, and will vary depending on the information that is available.

Prospectus [Line Items]

Risk [Text Block]

●

Affiliated Fund Risk. Affiliated fund risk is the risk that the Adviser may select investments for the Fund based on its own financial interests or other business considerations rather than the Fund’s interests. The Adviser may be subject to potential conflicts of interest in selecting the Underlying Funds because affiliated Underlying Funds pay an advisory fee to the Adviser based on their assets, the fees paid to the Adviser by some affiliated Underlying Funds may be higher than other Underlying Funds or the Underlying Funds may be in need of assets to enhance their appeal to other investors, liquidity and trading and/or to enable them to carry out their investment strategies. However, the Adviser is a fiduciary to the Fund and is legally obligated to act in the Fund’s best interest when selecting Underlying Funds.

Prospectus [Line Items]

Risk [Text Block]

●

Call Risk. During periods of falling interest rates, an issuer of a callable bond held by an Underlying Fund may “call” or repay the security before its stated maturity, and the Underlying Fund may have to reinvest the proceeds in securities with lower yields, which would result in a decline in the Fund’s performance, or in securities with greater risks or with other less favorable features

Prospectus [Line Items]

Risk [Text Block]

●

Concentration Risk. The Fund may be susceptible to an increased risk of loss, including losses due to adverse events that affect the Fund’s investments more than the market as a whole, to the extent that the Fund’s investments are concentrated in a particular issue, issuer or issuers, country, market segment, or asset class.

Prospectus [Line Items]

Risk [Text Block]

●

Cyber Security Risk. Cyber security risk is the risk of an unauthorized breach and access to the Fund’s assets, Fund or customer data (including private shareholder information), or proprietary information, or the risk of an incident occurring that causes the Fund, the Adviser, custodian, transfer agent, distributor and other service providers and financial intermediaries to suffer data breaches, data corruption or lose operational functionality or prevent the Fund’s investors from purchasing, redeeming or exchanging Shares or receiving distributions. While the Fund and the Adviser have established business continuity plans and risk management systems seeking to address system breaches or failures, there are inherent limitations in such plans and systems. Further, the Fund cannot control the cybersecurity plans and systems of the Fund’s service providers, market makers, or issuers of securities in which the Fund invests. The Fund and the Adviser have limited ability to prevent or mitigate cyber security incidents affecting third-party service providers, and such third-party service providers may have limited indemnification obligations to the Fund or the Adviser. Successful cyber-attacks or other cyber-failures or events affecting the Fund or its service providers may adversely impact and cause financial losses to the Fund or its shareholders. Issuers of securities in which the Fund invests are also subject to cyber security risks, and the value of these securities could decline if the issuers experience cyberattacks or other cyber-failures.

Prospectus [Line Items]

Risk [Text Block]

●

Fixed-Income Market Risk. The market value of a fixed-income security may decline due to general market conditions that are not specifically related to a particular issuer, such as real or perceived adverse economic conditions, changes in the outlook for corporate earnings, changes in interest or currency rates or adverse investor sentiment generally. The fixed-income securities market can be susceptible to increases in volatility and decreases in liquidity. Liquidity can decline unpredictably in response to overall economic conditions or credit tightening. Increases in volatility and decreases in liquidity may be caused by a rise in interest rates (or the expectation of a rise in interest rates). An unexpected increase in Fund redemption requests, including requests from shareholders who may own a significant percentage of the Fund’s Shares, which may be triggered by market turmoil or an increase in interest rates, could cause the Fund to sell its holdings at a loss or at undesirable prices and adversely affect the Fund’s Share price and increase the Fund’s liquidity risk, expenses and/or taxable distributions.

Prospectus [Line Items]

Risk [Text Block]

●

Income Risk. Under certain market conditions, the Fund may invest in Underlying Funds that are subject to income risk. The Fund’s income may decline when interest rates fall or if there are defaults in its portfolio. This decline can occur because the Fund may subsequently invest in lower-yielding securities as debt securities in its portfolio mature, are near maturity or are called, or the Fund otherwise needs to purchase additional debt securities.

Prospectus [Line Items]

Risk [Text Block]

●

Index Rebalance Risk. Pursuant to the methodology that the Index Provider uses to calculate and maintain the Underlying Index, the Fund may own a significant portion of the Underlying Funds included in the Underlying Index. Any Underlying Fund may be removed from the Underlying Index in the event that it does not comply its eligibility requirements. As a result, the Fund may be forced to sell shares of Underlying Funds at inopportune times or for prices other than at current market values or may elect not to sell such shares on the day that they are removed from the Underlying Index, due to market conditions or otherwise. Due to these factors, the variation between the Fund’s annual return and the return of the Underlying Index may increase significantly. Apart from scheduled rebalances, the Index Provider may carry out additional ad hoc rebalances to the Underlying Index to, for example, correct an error in the selection of constituents. When the Fund in turn rebalances its portfolio, any transaction costs and market exposure arising from such portfolio rebalancing will be borne by the Fund and its shareholders. Unscheduled rebalances may also expose the Fund to additional tracking error risk. Therefore, errors and additional ad hoc rebalances carried out by the Index Provider and/or the Index Calculator may increase the Fund’s costs and market exposure.

Prospectus [Line Items]

Risk [Text Block]

●

Interest Rate Risk. Interest rate risk is the risk of losses attributable to changes in interest rates. In general, if prevailing interest rates rise, the values of debt instruments tend to fall, and if interest rates fall, the values of debt instruments tend to rise. Changes in the value of a debt instrument usually will not affect the amount of income the Fund receives from it but will generally affect the value of your investment in the Fund. Changes in interest rates may also affect the liquidity of the Fund’s investments in debt instruments. In general, the longer the maturity or duration of a debt instrument, the greater its sensitivity to changes in interest rates. The Fund is subject to the risk that the income generated by its investments may not keep pace with inflation. Actions by governments and central banking authorities can result in increases or decreases in interest rates, which may negatively affect the value of debt instruments held by the Fund and have a negative impact on the Fund’s performance and NAV. Rising interest rates may prompt redemptions from the Fund, which may force the Fund to sell investments at a time when it is not advantageous to do so, which could result in losses. During periods of very low or negative interest rates, the Fund may be unable to maintain positive returns or pay dividends to Fund shareholders. Very low or negative interest rates may magnify interest rate risk. Changing interest rates, including rates that fall below zero, may have unpredictable effects on markets, result in heightened market volatility and detract from the Fund’s performance to the extent the Fund is exposed to such interest rates. Additionally, under certain market conditions in which interest rates are low and the market prices for portfolio securities have increased, the Fund may have a very low or even negative yield. A low or negative yield would cause the Fund to lose money in certain conditions and over certain time periods. An increase in interest rates will generally cause the value of securities held by the Fund to decline, may lead to heightened volatility in the fixed-income markets and may adversely affect the liquidity of certain fixed-income investments, including those held by the Fund. The historically low-interest rate environment in recent years heightens the risks associated with rising interest rates.

Prospectus [Line Items]

Risk [Text Block]

●

Liquidity Risk. Certain securities held by an Underlying Fund may be difficult (or impossible) to sell at the time and at the price the Adviser would like. As a result, an Underlying Fund may have to hold these securities longer than it would like and may forego other investment opportunities. There is the possibility that an Underlying Fund may lose money or be prevented from realizing capital gains if it cannot sell a security at a particular time and price.

Prospectus [Line Items]

Risk [Text Block]

●

Market Risk. Economies and financial markets throughout the world are becoming increasingly interconnected, which increases the likelihood that events or conditions in one country or region will adversely impact markets or issuers in other countries or regions. The value of the Fund and/or the Underlying Fund's investments may be negatively affected by adverse changes in overall economic or market conditions, such as the level of economic activity and productivity, unemployment and labor force participation rates, inflation or deflation (and expectations for inflation or deflation), interest rates, demand and supply for particular products or resources including labor, and debt levels and credit ratings, among other factors. Such adverse conditions may contribute to an overall economic contraction across entire economies or markets, which may negatively impact the profitability of issuers operating in those economies or markets. The Fund and the Underlying Funds subject to the risk that geopolitical events will disrupt securities markets and adversely affect global economies and markets. The Fund and the Underlying Funds’ NAV and market price may fluctuate significantly in response to these and other factors including economic, political, or financial events, public health crises (such as epidemics or pandemics), or other disruptive events (whether real, expected or perceived) in the U.S. and global markets. The Fund could lose money over short periods due to short-term market movements and over longer periods during more prolonged market downturns. As a result, an investor could lose money over short or long periods of time.

Prospectus [Line Items]

Risk [Text Block]

●

New Fund Risk. The Fund is a newly organized, management investment company with a limited operating history. In addition, there can be no assurance that the Fund will grow to, or maintain, an economically viable size, in which case the Board of Directors (the “Board”) of The RBB Fund, Inc. (the “Company”) may determine to liquidate the Fund.

Prospectus [Line Items]

Risk [Text Block]

●

Operational Risk. The Fund is exposed to operational risks arising from a number of factors, including, but not limited to, human error, processing and communication errors, errors of the Fund’s service providers, counterparties, or other third parties, failed or inadequate processes and technology or systems failures. The Fund and the Adviser seek to reduce these operational risks through controls and procedures. However, these measures do not address every possible risk and may be inadequate to address significant operational risks.

Prospectus [Line Items]

Risk [Text Block]

●

Premium/Discount Risk. The market price of the Fund’s Shares will generally fluctuate in accordance with changes in the Fund’s NAV as well as the relative supply of and demand for Shares on the exchange. The Adviser cannot predict whether Shares will trade below, at, or above their NAV because the Shares trade on the exchange at market prices and not at NAV. Price differences may be due, in large part, to the fact that supply and demand forces at work in the secondary trading market for Shares will be closely related, but not identical, to the same forces influencing the prices of the holdings of the Fund trading individually or in the aggregate at any point in time. However, given that Shares can only be purchased and redeemed in Creation Units, and only to and from broker-dealers and large institutional investors that have entered into participation agreements (unlike shares of closed-end funds, which frequently trade at appreciable discounts from, and sometimes at premiums to, their NAV), the Adviser believes that large discounts or premiums to the NAV of Shares should not be sustained. During stressed market conditions, the market for the Fund’s Shares may become less liquid in response to deteriorating liquidity in the market for the Fund’s underlying holdings, which could in turn lead to differences between the market price of the Fund’s Shares and their NAV and the bid/ask spread on the Fund’s Shares may widen.

Prospectus [Line Items]

Risk [Text Block]

●

Reinvestment Risk. Reinvestment risk is the risk that the Fund’s portfolio will decline if and when the Fund reinvests the proceeds from the disposition of its portfolio securities at market interest rates that are below the portfolio’s current earnings rate. A decline in income could negatively affect the market price of the Shares.

Prospectus [Line Items]

Risk [Text Block]

●

Sector Risk. To the extent the Fund invests more heavily in particular sectors of the economy, its performance will be especially sensitive to developments that significantly affect those sectors.

Prospectus [Line Items]

Risk [Text Block]

●

Tax Risk. Because the Fund is expected to invest in the Underlying Funds, distributions of short-term capital gains by an Underlying Fund will be recognized as ordinary income by the Fund and would not be offset by the Fund's capital loss carryforwards, if any. Capital loss carryforwards of an Underlying Fund, if any, will not be available to offset net capital gains of the Fund. Further, the Fund’s realized losses on sales of shares of an Underlying Fund may be indefinitely or permanently deferred as "wash sales" to the extent it reacquires shares of the same Underlying Fund within the 61-day period beginning 30 days prior to the disposition date.

Prospectus [Line Items]

Risk [Text Block]

●

U.S. Government Obligations Risk. While U.S. Treasury obligations are backed by the “full faith and credit” of the U.S. Government, such securities are nonetheless subject to credit risk (i.e., the risk that the U.S. Government may be, or be perceived to be, unable or unwilling to honor its financial obligations, such as making payments). Securities issued or guaranteed by federal agencies or authorities and U.S. Government-sponsored instrumentalities or enterprises may or may not be backed by the full faith and credit of the U.S. Government.

Prospectus [Line Items]

Risk [Text Block]

●

Duration Risk. Duration is a measure of the price sensitivity of a debt security or portfolio to interest rate changes. Duration risk is the risk that longer-duration debt securities will be more volatile and thus more likely to decline in price, and to a greater extent, in a rising interest rate environment than shorter-duration debt securities.

Prospectus [Line Items]

Risk [Text Block]

●

Market Price Risk. Fund Shares are listed for trading on an exchange and are bought and sold in the secondary market at market prices. The market prices of Shares will fluctuate, in some cases materially, in response to changes in the NAV and supply and demand for Shares. As a result, the trading prices of Shares may deviate significantly from the NAV during periods of market volatility. The Adviser cannot predict whether Shares will trade above, below or at their NAV. Given the fact that Shares can be created and redeemed in Creation Units (defined below), the Adviser believes that large discounts or premiums to the NAV of Shares should not be sustained in the long-term. If market makers exit the business or are unable to continue making markets in Fund Shares, Shares may trade at a discount to NAV like closed-end fund shares and may even face delisting (that is, investors would no longer be able to trade Shares in the secondary market). Further, while the creation/redemption feature is designed to make it likely that Shares normally will trade close to the value of the Fund’s holdings, disruptions to creations and redemptions, including disruptions at market makers, APs or market participants, or during periods of significant market volatility, may result in market prices that differ significantly from the value of the Fund’s holdings. Although market makers will generally take advantage of differences between the NAV and the market price of Fund Shares through arbitrage opportunities, there is no guarantee that they will do so. In addition, the securities held by the Fund may be traded in markets that close at a different time than the exchange on which the Fund’s Shares trade. Liquidity in those securities may be reduced after the applicable closing times. Accordingly, during the time when the exchange is open but after the applicable market closing, fixing or settlement times, bid-ask spreads and the resulting premium or discount to the Shares’ NAV is likely to widen. Further, secondary markets may be subject to irregular trading activity, wide bid-ask spreads and extended trade settlement periods, which could cause a material decline in the Fund’s NAV. The Fund’s investment results are measured based upon the daily NAV of the Fund. Investors purchasing and selling Shares in the secondary market may not experience investment results consistent with those experienced by those APs creating and redeeming Shares directly with the Fund.

Prospectus [Line Items]

Risk [Text Block]

●

Risk of Investing in the U.S. Certain changes in the U.S. economy, such as when the U.S. economy weakens or when its financial markets decline, may have an adverse effect on the securities to which the Fund has exposure.

Prospectus [Line Items]

Risk [Text Block]

As a result, you may lose money on your investment in the Fund, and there can be no assurance that the Fund will achieve its investment objective.

Prospectus [Line Items]

Risk [Text Block]

●

Asset Class Risk. The securities and other assets in the Underlying Index or in the Fund’s portfolio may underperform in comparison to financial markets generally, a particular financial market, another index, or other asset classes.

Prospectus [Line Items]

Risk [Text Block]

●

Concentration Risk. The Fund may be susceptible to an increased risk of loss, including losses due to adverse events that affect the Fund’s investments more than the market as a whole, to the extent that the Fund’s investments are concentrated in a particular issue, issuer or issuers, country, market segment, industries, project types, or asset class.

Prospectus [Line Items]

Risk [Text Block]

●

Cyber Security Risk. Cyber security risk is the risk of an unauthorized breach and access to the Fund’s assets, Fund or customer data (including private shareholder information), or proprietary information, or the risk of an incident occurring that causes the Fund, the Adviser, custodian, transfer agent, distributor and other service providers and financial intermediaries to suffer data breaches, data corruption or lose operational functionality or prevent the Fund’s investors from purchasing, redeeming or exchanging Shares or receiving distributions. While the Fund and the Adviser have established business continuity plans and risk management systems seeking to address system breaches or failures, there are inherent limitations in such plans and systems. Further, the Fund cannot control the cybersecurity plans and systems of the Fund’s service providers, market makers, or issuers of securities in which the Fund invests. The Fund and the Adviser have limited ability to prevent or mitigate cyber security incidents affecting third-party service providers, and such third-party service providers may have limited indemnification obligations to the Fund or the Adviser. Successful cyber-attacks or other cyber-failures or events affecting the Fund or its service providers may adversely impact and cause financial losses to the Fund or its shareholders. Issuers of securities in which the Fund invests are also subject to cyber security risks, and the value of these securities could decline if the issuers experience cyberattacks or other cyber-failures.

Prospectus [Line Items]

Risk [Text Block]

●

Fixed-Income Market Risk. The market value of a fixed-income security may decline due to general market conditions that are not specifically related to a particular issuer, such as real or perceived adverse economic conditions, changes in the outlook for corporate earnings, changes in interest or currency rates or adverse investor sentiment generally. The fixed-income securities market can be susceptible to increases in volatility and decreases in liquidity. Liquidity can decline unpredictably in response to overall economic conditions or credit tightening. Increases in volatility and decreases in liquidity may be caused by a rise in interest rates (or the expectation of a rise in interest rates). An unexpected increase in Fund redemption requests, including requests from shareholders who may own a significant percentage of the Fund’s Shares, which may be triggered by market turmoil or an increase in interest rates, could cause the Fund to sell its holdings at a loss or at undesirable prices and adversely affect the Fund’s Share price and increase the Fund’s liquidity risk, expenses and/or taxable distributions.

Prospectus [Line Items]

Risk [Text Block]

●

Income Risk. The Fund’s income may decline if interest rates fall. This decline in income can occur because the Fund may subsequently invest in lower yielding bonds as bonds in its portfolio mature, are near maturity or are called, bonds in the Underlying Index are substituted, or the Fund otherwise needs to purchase additional bonds.

Prospectus [Line Items]

Risk [Text Block]

●

Index Rebalance Risk. Pursuant to the methodology that the Index Provider uses to calculate and maintain the Underlying Index, the Fund may own a significant portion of the Underlying Funds included in the Underlying Index. Any Underlying Fund may be removed from the Underlying Index in the event that it does not comply its eligibility requirements. As a result, the Fund may be forced to sell shares of Underlying Funds at inopportune times or for prices other than at current market values or may elect not to sell such shares on the day that they are removed from the Underlying Index, due to market conditions or otherwise. Due to these factors, the variation between the Fund’s annual return and the return of the Underlying Index may increase significantly. Apart from scheduled rebalances, the Index Provider may carry out additional ad hoc rebalances to the Underlying Index to, for example, correct an error in the selection of constituents. When the Fund in turn rebalances its portfolio, any transaction costs and market exposure arising from such portfolio rebalancing will be borne by the Fund and its shareholders. Unscheduled rebalances may also expose the Fund to additional tracking error risk. Therefore, errors and additional ad hoc rebalances carried out by the Index Provider and/or the Index Calculator may increase the Fund’s costs and market exposure.

Prospectus [Line Items]

Risk [Text Block]

●

Interest Rate Risk. Interest rate risk is the risk of losses attributable to changes in interest rates. In general, if prevailing interest rates rise, the values of debt instruments tend to fall, and if interest rates fall, the values of debt instruments tend to rise. Changes in the value of a debt instrument held by an Underlying Fund usually will not affect the amount of income the Fund receives from it but will generally affect the value of your investment in the Fund. Changes in interest rates may also affect the liquidity of an Underlying Fund’s investments in debt instruments. In general, the longer the maturity or duration of a debt instrument, the greater its sensitivity to changes in interest rates. The Fund is subject to the risk that the income generated by an Underlying Fund’s investments may not keep pace with inflation. Actions by governments and central banking authorities can result in increases or decreases in interest rates, which may negatively affect the value of debt instruments held by the Fund and have a negative impact on the Fund’s performance and NAV. Rising interest rates may prompt redemptions from the Fund, which may force the Fund to sell investments at a time when it is not advantageous to do so, which could result in losses. During periods of very low or negative interest rates, the Fund may be unable to maintain positive returns or pay dividends to Fund shareholders. Very low or negative interest rates may magnify interest rate risk. Changing interest rates, including rates that fall below zero, may have unpredictable effects on markets, result in heightened market volatility and detract from the Fund’s performance to the extent the Fund is exposed to such interest rates. Additionally, under certain market conditions in which interest rates are low and the market prices for portfolio securities have increased, the Fund may have a very low or even negative yield. A low or negative yield would cause the Fund to lose money in certain conditions and over certain time periods. An increase in interest rates will generally cause the value of securities held by Underlying Funds to decline, may lead to heightened volatility in the fixed-income markets and may adversely affect the liquidity of certain fixed-income investments, including those held by Underlying Funds. The historically low-interest rate environment in recent years heightens the risks associated with rising interest rates.

Prospectus [Line Items]

Risk [Text Block]

●

Liquidity Risk. Certain securities held by the Fund may be difficult (or impossible) to sell at the time and at the price the Adviser would like. As a result, the Fund may have to hold these securities longer than it would like and may forego other investment opportunities. There is the possibility that the Fund may lose money or be prevented from realizing capital gains if it cannot sell a security at a particular time and price.

Prospectus [Line Items]

Risk [Text Block]

●

Market Risk. Economies and financial markets throughout the world are becoming increasingly interconnected, which increases the likelihood that events or conditions in one country or region will adversely impact markets or issuers in other countries or regions. The value of the Fund and/or an Underlying Fund’s investments may be negatively affected by adverse changes in overall economic or market conditions, such as the level of economic activity and productivity, unemployment and labor force participation rates, inflation or deflation (and expectations for inflation or deflation), interest rates, demand and supply for particular products or resources including labor, and debt levels and credit ratings, among other factors. Such adverse conditions may contribute to an overall economic contraction across entire economies or markets, which may negatively impact the profitability of issuers operating in those economies or markets. The Fund and/or an Underlying Fund is subject to the risk that geopolitical events will disrupt securities markets and adversely affect global economies and markets. The Fund and/or an Underlying Fund’s NAV and market price may fluctuate significantly in response to these and other factors including economic, political, or financial events, public health crises (such as epidemics or pandemics), or other disruptive events (whether real, expected or perceived) in the U.S. and global markets. The Fund could lose money over short periods due to short-term market movements and over longer periods during more prolonged market downturns. As a result, an investor could lose money over short or long periods of time.

Prospectus [Line Items]

Risk [Text Block]

●

New Fund Risk. The Fund is a newly organized, management investment company with a limited operating history. In addition, there can be no assurance that the Fund will grow to, or maintain, an economically viable size, in which case the Board of Directors (the “Board”) of The RBB Fund, Inc. (the “Company”) may determine to liquidate the Fund.

Prospectus [Line Items]

Risk [Text Block]

●

Operational Risk. The Fund is exposed to operational risks arising from a number of factors, including, but not limited to, human error, processing and communication errors, errors of the Fund’s service providers, counterparties, or other third parties, failed or inadequate processes and technology or systems failures. The Fund and the Adviser seek to reduce these operational risks through controls and procedures. However, these measures do not address every possible risk and may be inadequate to address significant operational risks.

Prospectus [Line Items]

Risk [Text Block]

●

Premium/Discount Risk. The market price of the Fund’s Shares will generally fluctuate in accordance with changes in the Fund’s NAV as well as the relative supply of and demand for Shares on the exchange. The Adviser cannot predict whether Shares will trade below, at, or above their NAV because the Shares trade on the exchange at market prices and not at NAV. Price differences may be due, in large part, to the fact that supply and demand forces at work in the secondary trading market for Shares will be closely related, but not identical, to the same forces influencing the prices of the holdings of the Fund trading individually or in the aggregate at any point in time. However, given that Shares can only be purchased and redeemed in Creation Units, and only to and from broker-dealers and large institutional investors that have entered into participation agreements (unlike shares of closed-end funds, which frequently trade at appreciable discounts from, and sometimes at premiums to, their NAV), the Adviser believes that large discounts or premiums to the NAV of Shares should not be sustained. During stressed market conditions, the market for the Fund’s Shares may become less liquid in response to deteriorating liquidity in the market for the Fund’s underlying holdings, which could in turn lead to differences between the market price of the Fund’s Shares and their NAV and the bid/ask spread on the Fund’s Shares may widen.

Prospectus [Line Items]

Risk [Text Block]

●

Reinvestment Risk. Reinvestment risk is the risk that income from the Fund’s portfolio will decline if and when the Fund reinvests the proceeds from the disposition of its portfolio securities at market interest rates that are below the portfolio's current earnings rate. A decline in income could negatively affect the market price of the Shares.

Prospectus [Line Items]

Risk [Text Block]

●

Sector Risk. To the extent the Fund invests more heavily in particular sectors of the economy, its performance will be especially sensitive to developments that significantly affect those sectors.

Prospectus [Line Items]

Risk [Text Block]

●

Tax Risk. Because the Fund is expected to invest in the Underlying Funds, distributions of short-term capital gains by an Underlying Fund will be recognized as ordinary income by the Fund and would not be offset by the Fund's capital loss carryforwards, if any. Capital loss carryforwards of an Underlying Fund, if any, will not be available to offset net capital gains of the Fund. Further, the Fund’s realized losses on sales of shares of an Underlying Fund may be indefinitely or permanently deferred as "wash sales" to the extent it reacquires shares of the same Underlying Fund within the 61-day period beginning 30 days prior to the disposition date.

Prospectus [Line Items]

Risk [Text Block]

●

U.S. Government Obligations Risk. While U.S. Treasury obligations are backed by the “full faith and credit” of the U.S. Government, such securities are nonetheless subject to credit risk (i.e., the risk that the U.S. Government may be, or be perceived to be, unable or unwilling to honor its financial obligations, such as making payments). Securities issued or guaranteed by federal agencies or authorities and U.S. Government-sponsored instrumentalities or enterprises may or may not be backed by the full faith and credit of the U.S. Government.

Prospectus [Line Items]

Risk [Text Block]

●

Duration Risk. Duration is a measure of the price sensitivity of a debt security or portfolio to interest rate changes. Duration risk is the risk that longer- duration debt securities will be more volatile and thus more likely to decline in price, and to a greater extent, in a rising interest rate environment than shorter-duration debt securities.

Prospectus [Line Items]

Risk [Text Block]

●

Market Price Risk. Fund Shares are listed for trading on an exchange and are bought and sold in the secondary market at market prices. The market prices of Shares will fluctuate, in some cases materially, in response to changes in the NAV and supply and demand for Shares. As a result, the trading prices of Shares may deviate significantly from the NAV during periods of market volatility. The Adviser cannot predict whether Shares will trade above, below or at their NAV. Given the fact that Shares can be created and redeemed in Creation Units (defined below), the Adviser believes that large discounts or premiums to the NAV of Shares should not be sustained in the long-term. If market makers exit the business or are unable to continue making markets in Fund Shares, Shares may trade at a discount to NAV like closed-end fund shares and may even face delisting (that is, investors would no longer be able to trade Shares in the secondary market). Further, while the creation/redemption feature is designed to make it likely that Shares normally will trade close to the value of the Fund’s holdings, disruptions to creations and redemptions, including disruptions at market makers, APs or market participants, or during periods of significant market volatility, may result in market prices that differ significantly from the value of the Fund’s holdings. Although market makers will generally take advantage of differences between the NAV and the market price of Fund Shares through arbitrage opportunities, there is no guarantee that they will do so. In addition, the securities held by the Fund may be traded in markets that close at a different time than the exchange on which the Fund’s Shares trade. Liquidity in those securities may be reduced after the applicable closing times. Accordingly, during the time when the exchange is open but after the applicable market closing, fixing or settlement times, bid-ask spreads and the resulting premium or discount to the Shares’ NAV is likely to widen. Further, secondary markets may be subject to irregular trading activity, wide bid-ask spreads and extended trade settlement periods, which could cause a material decline in the Fund’s NAV. The Fund’s investment results are measured based upon the daily NAV of the Fund. Investors purchasing and selling Shares in the secondary market may not experience investment results consistent with those experienced by those APs creating and redeeming Shares directly with the Fund.

Prospectus [Line Items]

Risk [Text Block]

●

Counterparty Risk. The Underlying Funds may engage in transactions in securities and financial instruments that involve counterparties. Counterparty risk is the risk that a counterparty (the other party to a transaction or an agreement or the party with whom the Underlying Fund executes transactions) to a transaction with the Underlying Fund may be unable or unwilling to make timely principal, interest or settlement payments, or otherwise honor its obligations.

Prospectus [Line Items]

Risk [Text Block]

●

Mortgage-Backed and Asset-Backed Securities Risk. The Fund may invest in Underlying Funds that invest in mortgage- and asset-backed securities, which are subject to call (prepayment) risk, reinvestment risk and extension risk. In addition, these securities are susceptible to an unexpectedly high rate of defaults on the mortgages held by a mortgage pool, which may adversely affect their value. The risk of such defaults depends on the quality of the mortgages underlying such security, the credit quality of its issuer or guarantor, and the nature and structure of its credit support. For example, the risk of default generally is higher in the case of mortgage pools that include subprime mortgages, which are loans made to borrowers with weakened credit histories or with lower capacity to make timely mortgage payments.

Prospectus [Line Items]

Risk [Text Block]

●

When-Issued Securities Risk. The Fund may invest in Underlying Funds that purchase securities on a when-issued or forward commitment basis. The purchase price of such securities is typically fixed at the time of the commitment, with delivery and payment taking place in the future. At the time of delivery of the securities, the value may be more or less than the purchase or sale price. Purchase of securities on a when-issued or forward commitment basis may give rise to investment leverage, and may result in increased volatility of the Underlying Fund’s NAV. Default by, or bankruptcy of, a counterparty to a when-issued transaction would expose the Underlying Fund to possible losses because of an adverse market action, expenses or delays in connection with the purchase or sale of the pools specified in such transaction. The Financial Industry Regulatory Authority, Inc. (“FINRA”) Rules impose mandatory margin requirements for certain types of when-issued or forward commitment transactions, with limited exceptions. Such transactions require mandatory collateralization, which may increase the cost of such transactions and impose added operational complexity.

Prospectus [Line Items]