11. Equity Compensation Plans:

All of our outstanding stock options, restricted stock awards, deferred stock units, and PSUs are covered under our 2021 Incentive Plan or our 2013 Incentive Plan. Awards under our 2021 Incentive Plan  may include one or more of the following types: (i) stock options (both nonqualified and incentive stock options), (ii) stock appreciation rights, (iii) restricted stock, (iv) restricted stock units, (v) performance awards, (vi) other share-based awards, and (vii) cash. Employees, non-employee directors, and consultants are eligible for awards under our 2021 Incentive Plan. We transferred common stock under these plans from our treasury shares. As of June 30, 2025, there were 12,172,972 shares of common stock reserved and available for future issuance under our 2021 Incentive Plan. Cash received from stock option exercises for the six months ended  June 30, 2025 and 2024 was $47.6 million and $63.2 million, respectively.

We grant equity awards to our key employees. The nonqualified stock options have an exercise price equal to the adjusted closing price of our common stock on the grant date, with a ten-year contractual term. The fair value of the restricted stock is determined using the closing price of our common stock on the grant date. The restricted stock is not assignable or transferable until it becomes vested. PSUs vest at the end of a three-year performance period, subject to the recipient’s continued service. Each PSU represents the right to receive one share of our common stock and the ultimate realization is based on our achievement of certain market and financial performance criteria and may range from 0% to 200% of the recipient’s target levels of 100% established on the grant date. The fair value of PSUs based on market conditions is determined on the grant date using the Monte Carlo Simulation model. The fair value of PSUs based on financial performance conditions is determined using the closing price of our common stock on the grant date. We recognize the expense of the equity awards ratably over the vesting period, which could be up to four years.

In January 2025, we granted 212,590 nonqualified stock options, 125,835 shares of restricted stock, and 46,225 PSUs to key employees. The nonqualified stock options and restricted stock have a graded service vesting period of four years. The PSUs granted consisted of 28,822 PSUs that are based on the achievement of relative total shareholder return as compared to the companies that comprise the S&P 500 index ("TSR-based PSUs") and 17,403 PSUs that are tied to the achievement of certain financial performance conditions, namely incremental return on invested capital (“ROIC-based PSUs”). Each of the TSR-based PSUs and ROIC-based PSUs have a three-year performance period, subject to the recipients' continued service. The grant date fair value of the ROIC-based PSUs is determined using the closing price of our common stock on the grant date. The related performance condition is driven by the incremental return on invested capital based on net operating profit. The ultimate realization of the PSUs may range from 0% to 200% of the recipient’s target levels established on the grant date. 

A summary of the status of the stock options, restricted stock, and PSUs awarded under our 2021 and 2013 Incentive Plans as of December 31, 2024 and June 30, 2025 and changes during the interim period are presented below:

The fair value of the stock options granted was estimated using a Black-Scholes valuation model that uses the weighted average assumptions noted in the following table for the six months ended June 30, 2025 and 2024:

The expected term for the stock options granted was estimated based on studies of historical experience and projected exercise behavior. However, for certain awards granted, for which no historical exercise pattern exists, the expected term was estimated using the simplified method. The risk-free interest rate is based on the yield of U.S. Treasury zero coupon securities with a maturity equal to the expected term of the equity award. The volatility factor is calculated using historical daily closing prices over the most recent period commensurate with the expected term of the stock option awards. The expected dividend yield was based on our expected annual dividend rate on the date of grant.

Intrinsic value for stock options is calculated based on the exercise price of the underlying awards and the adjusted closing price of our common stock as of the reporting date. Excess tax benefits from stock-based compensation were recorded as income tax benefit in our condensed consolidated statements of operations. This tax benefit is calculated as the excess of the intrinsic value of options exercised and restricted stock lapsed in excess of compensation recognized for financial reporting purposes. The weighted average remaining contractual terms were 5.8 years and 4.7 years for the outstanding and exercisable stock options, respectively, as of June 30, 2025.

As of  June 30, 2025, there was $110.1 million of total unrecognized compensation costs, exclusive of the impact of vesting upon retirement eligibility, related to nonvested stock-based compensation arrangements granted under our 2021 and 2013 Incentive Plans. That cost is expected to be recognized over a weighted average period of 2.6 years.

Our U.K. Sharesave Plan offers qualifying employees in the United Kingdom the opportunity to own shares of our common stock. Employees who elect to participate are granted stock options, of which the exercise price is equal to the average of the closing price on the five trading days immediately preceding the plan invitation date discounted by 5%, and enter into a savings contract, the proceeds of which are then used to exercise the options upon the three-year maturity of the savings contract. As of June 30, 2025, there were 439,392 shares of common stock reserved and available for future issuance under our U.K. Sharesave Plan.

Our ESPP offers eligible employees the opportunity to purchase shares of our common stock at a discount of its fair market value at the time of purchase. During the six months ended June 30, 2025 and 2024, we issued 8,659 and 8,928 shares of common stock at a weighted discounted price of $288.78 and $238.01 for the ESPP, respectively. As of June 30, 2025, there were 1,151,635 shares of common stock reserved and available for future issuance under our ESPP.