Stock-based compensation expense for each employee and director is presented in the same statement of operations caption as their cash compensation. Stock-based compensation expense by statement of operations caption and the related income tax benefit were as follows:


	Three Months Ended June 30,				Six Months Ended June 30,
(In thousands)	2024		2023		2024		2023
Cost of sales	$	20	$	26	$	47	$	62
Research and development expenses	142		251		373		534
Selling, general and administrative expenses:
Employees	1,204		1,666		2,755		3,672
Outside directors	94		215		189		430
Total employee and director stock-based compensation expense	$	1,460	$	2,158	$	3,364	$	4,698
Income tax benefit	$	220	$	337	$	507	$	747

Non-vested restricted stock award activity was as follows:


	Shares (in thousands)	Weighted-Average Grant Date Fair Value
Non-vested at December 31, 2023	486	$	21.66
Granted	322	10.38
Vested	(220)	25.60
Forfeited	(17)	17.23
Non-vested at June 30, 2024	571	$	13.92

As of June 30, 2024, we expect to recognize $6.9 million of total unrecognized pre-tax stock-based compensation expense related to non-vested restricted stock awards over a weighted-average life of 2.0 years.


	Shares (in thousands)	Weighted-Average Grant Date Fair Value
Non-vested at December 31, 2023	—	$	—
Granted	116	4.72
Vested	—	—
Forfeited	—	—
Non-vested at June 30, 2024	116	$	4.72

The assumptions we utilized in the Monte Carlo simulation model and the resulting weighted average fair value of performance stock grants were the following:


	Three Months Ended June 30,			Six Months Ended June 30,
	2024			2024
Weighted average fair value of grants	$	—		$	4.72
Risk-free interest rate	—		%	4.08		%
Expected volatility	—		%	57.00		%
Expected life in years	0.00			2.73

As of June 30, 2024, we expect to recognize $0.5 million of total unrecognized pre-tax stock-based compensation expense related to non-vested performance stock awards over a weighted-average life of 2.3 years.


	Number of Options (in thousands)	Weighted-Average Exercise Price		Weighted-Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2023	901	$	38.78
Granted	—	—
Exercised	—	—			$	—
Forfeited/canceled/expired	(122)	58.52
Outstanding at June 30, 2024 (1)	779	$	35.67	3.62	$	—
Vested and expected to vest at June 30, 2024 (1)	779	$	35.67	3.62	$	—
Exercisable at June 30, 2024 (1)	612	$	38.18	3.07	$	—

(1)The aggregate intrinsic value represents the total pre-tax value (the difference between our closing stock price on the last trading day of the first quarter of 2024 and the exercise price, multiplied by the number of in-the-money options) that would have been received by the option holders had they all exercised their options on June 30, 2024. This amount will change based on the fair market value of our stock.

The assumptions we utilized in the Black-Scholes option pricing model and the resulting weighted average fair value of stock option grants were the following:


	Three Months Ended June 30,			Six Months Ended June 30,
	2023			2023
Weighted average fair value of grants	$	—		$	10.83
Risk-free interest rate	—		%	3.86		%
Expected volatility	—		%	45.89		%
Expected life in years	0.00			4.70

As of June 30, 2024, we expect to recognize $1.7 million of total unrecognized pre-tax stock-based compensation expense related to non-vested stock options over a remaining weighted-average life of 1.4 years.