A summary of shares available for grant under the Company’s plans is as follows:


	Shares Available for Grant
Total shares available for grant as of December 31, 2025		9,733,628
Nonvested equity stock and stock units granted (1)		(25,498	)
Nonvested equity stock and stock units forfeited (1)		375,092
Total shares available for grant as of March 31, 2026		10,083,222

(1)

For purposes of determining the number of shares available for grant under the 2015 Equity Incentive Plan against the maximum number of shares authorized, each restricted stock unit granted prior to April 27, 2023 reduces the number of shares available for grant by 1.5 shares and each restricted stock unit forfeited increases shares available for grant by 1.5 shares. Each restricted stock unit granted on or after April 27, 2023 reduces the number of shares available for grant by 1.0 share and each restricted stock unit forfeited increases shares available for grant by 1.0 share.

No purchases were made under the 2015 Employee Stock Purchase Plan (“2015 ESPP”) during the three months ended March 31, 2026 and 2025. As of March 31, 2026, approximately 2.1 million shares under the 2015 ESPP remained available for issuance.

For the three months ended March 31, 2026 and 2025, the Company maintained stock plans covering a broad range of potential equity grants, including stock options, nonvested equity stock and equity stock units and performance-based instruments. In addition, the Company sponsors the 2015 ESPP, whereby eligible employees are entitled to purchase common stock semi-annually, by means of limited payroll deductions, at a 15% discount from the fair market value of the common stock as of specific dates.

Stock-based compensation expense recorded in the Unaudited Condensed Consolidated Statements of Income was as follows:


	Three Months Ended March 31,
(In thousands)	2026		2025
Cost of revenue	$	139	$	162
Research and development		5,254		4,511
Sales, general and administrative		6,060		6,710
Total	$	11,453	$	11,383

The Company grants nonvested equity stock units to officers, employees and directors. These awards have a service condition, generally a service period of four years, except in the case of grants to directors, for which the service period is one year. The Company also grants performance unit awards to certain company executive officers with vesting subject to the achievement of certain performance and/or market conditions. The ultimate number of performance units that can be earned can range from 0% to 200% of target depending on performance relative to target over the applicable period. The shares earned will vest on the third or fourth anniversary of the date of grant. The Company’s shares available for grant have been reduced to reflect the shares that could be earned at the maximum target.

Unrecognized stock-based compensation related to all nonvested equity stock grants, net of estimated forfeitures, was approximately $77.1 million as of March 31, 2026. This amount is expected to be recognized over a weighted-average period of 2.3 years.

The following table reflects the activity related to nonvested equity stock and stock units for the three months ended March 31, 2026:


Nonvested Equity Stock and Stock Units	Shares			Weighted- Average Grant-Date Fair Value
Nonvested as of December 31, 2025		2,881,829		$	51.91
Granted		25,498		$	107.35
Vested		(574,401	)	$	44.42
Forfeited		(140,113	)	$	47.39
Nonvested as of March 31, 2026		2,192,813		$	54.81