We maintain two stockholder approved plans for the issuance of stock-based compensation awards to our employees and Board of Director members: (i) the 2019 Equity Incentive Plan, as amended (the “Equity Incentive Plan”), and (ii) the 1998 Stock Option Plan, as amended (the “Stock Option Plan”).


	Three months ended June 30,				Six months ended June 30,
	2025		2024		2025		2024
Equity-classified	$	579	$	242	$	938	$	516
Liability-classified (1)	137		16		137		16
	$	716	$	258	$	1,075	$	532

The Stock Option Plan provides for the granting of incentive and non-qualified stock options to our employees for up to 1,000,000 shares of common stock. After consideration of the activity described in the table below, a total of 395,669 shares remained available for grant under the Stock Option Plan as of June 30, 2025. The last date that grants can be made under the Stock Option Plan is February 28, 2026. A summary of all option activity during the six months ended June 30, 2025 is presented below:


	Number of Shares Underlying Stock Options	Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (years)	Aggregate Intrinsic Value
Outstanding, December 31, 2024	113,751	$	20.44	5.84	$	747
Granted	40,250	$	22.19		$	—
Exercised	(5,267)	$	10.58		$	76
Canceled/Forfeited	(5,333)	$	23.24		$	16
Expired	(23,167)	$	22.90		$	—
Outstanding, June 30, 2025	120,234	$	20.86	7.73	$	634
Exercisable, June 30, 2025	49,819	$	19.79	5.52	$	339


Range of Exercise Prices:	Options Outstanding				Options Exercisable
	Shares	Weighted Average Remaining Contractual Life (years)	Weighted Average Exercise Price		Shares	Weighted Average Exercise Price
$0.01-$18.00	24,234	6.79	$	10.76	20,067	$	10.95
$18.01-$26.00	79,250	9.30	$	22.41	13,002	$	22.66
$26.01-$30.00	16,750	1.63	$	28.15	16,750	$	28.15
	120,234	7.73	$	20.86	49,819	$	19.79


	Shares	Weighted Average Grant Date Fair Value Per Share
Unvested, December 31, 2024	48,998	$	11.35
Granted	40,250	$	12.06
Vested	(14,833)	$	11.33

Canceled/Forfeited	(4,000)	$	12.46
Unvested, June 30, 2025	70,415	$	11.70

As of June 30, 2025, there was a total of approximately $0.6 million of unrecognized compensation cost related to unvested options which is expected to be recognized over the next 2.33 years.

On June 5, 2025, our stockholders approved an amendment to the Equity Incentive Plan (the “Amendment”) to increase the number of shares available by 500,000 shares up to a total of 1,650,000 shares of common stock for issuance in the form of awards for: (i) stock options, (ii) stock appreciation rights, (iii) restricted awards in the form of restricted stock and restricted stock units (“RSUs”), (iv) performance share awards, including performance share units (“PSUs”) and (v) other equity-based awards. In addition, the Amendment extended the term of the Equity Incentive Plan by five years to June 20, 2034. After consideration of the activity described in detail below, a total of 643,514 shares remained available for grant under the Equity Incentive Plan as of June 30, 2025.


	Number of Shares	Weighted Average Grant Date Fair Value		Weighted Average Remaining Contractual Life (years)	Aggregate Intrinsic Value
Outstanding, December 31, 2024	131,183	$	16.39	5.15	$	3,516
Granted	69,672	$	22.67		$	1,579
Vested	(53,094)	$	15.35		$	1,327
Canceled/Forfeited	(910)	$	22.19		$	17
Outstanding, June 30, 2025	146,851	$	19.71	4.27	$	3,790

As of June 30, 2025, there was a total of approximately $2.1 million of unrecognized compensation cost related to unvested restricted stock and RSUs which is expected to be recognized over the next 2.12 years.

The 2025 and 2024 grants of RSUs to the independent Board members that can be settled in cash represent liability-classified awards. Compensation expense associated with these awards is based upon the fair value of NGS common stock at each reporting period relative to that portion of the service period that has passed. Accordingly, the compensation expense is variable in nature.


	Number of Shares	Weighted Average Grant Date Fair Value		Weighted Average Remaining Contractual Life (years)	Aggregate Intrinsic Value
Outstanding, December 31, 2024	15,069	$	19.51	0.50	$	294
Granted	13,368	$	24.69		$	330
Vested	(8,430)	$	19.57		$	165
Canceled/Forfeited	(2,810)	$	19.57		$	55
Outstanding, June 30, 2025	17,197	$	23.50	0.78	$	445

The potential payout for the PSU awards is based upon performance for a three-year period ending December 31, 2026 for the 2024 grants and December 31, 2027 for the 2025 grants measured against relative total shareholder return (“TSR”) compared to a peer group of companies as established by the Compensation Committee. The PSU award payout ranges from zero (if the Company ranks below the 31.25 percentile) and up to 200% (if the Company ranks first) based upon our relative TSR performance ranking (subject to certain caps based on absolute TSR as defined in the PSU agreements).

With respect to vesting, the PSUs have both a service condition and a market condition. Due to the presence of the TSR measurement for the common equity of the peer companies, including NGS common stock, which is deemed a “market condition,” the grant-date fair values of the PSUs have been determined using a binomial pricing model, or a Monte Carlo simulation model.

The following table summarizes the weighted average grant date fair values of PSUs granted and the assumptions used in the Monte Carlo simulation model for the determination of the grant date fair values of our PSUs granted during the six months ended June 30, 2025:


	Number of Shares	Weighted Average Grant Date Fair Value		Weighted Average Remaining Contractual Life (years)	Aggregate Intrinsic Value
Outstanding, December 31, 2024	56,764	$	22.47	2.22	$	—
Granted	39,434	$	28.05		$	—
Vested	—				$	—
Canceled/Forfeited	—				$	—
Outstanding, June 30, 2025	96,198	$	24.76	2.38	$	—

As of June 30, 2025, there was a total of approximately $1.8 million of unrecognized compensation cost related to the unvested portion of the PSUs which is expected to be recognized over the next 2.13 years.