The Company recognized total stock-based compensation expense during the three months ended March 31, 2024 and 2023 as follows (table in thousands):


	Three Months Ended March 31,
		2024		2023
Service-based awards:

Restricted Stock Units		$	118	$	45
Stock Option Awards		133		148






Total		$	251	$	193

A summary of the Company’s performance based restricted stock awards during the three months ended March 31, 2024 is as follows:


Performance Based Restricted Stock Awards	Number of Shares	Weighted Average Grant-Date Fair Value
Unvested at January 1, 2024	891	$	62.70

Unvested at March 31, 2024	891	$	62.70

Performance-based restricted stock awards are measured based on their fair value on the date of grant and amortized over the vesting period of 20 months. As of March 31, 2024, there is no unrecognized stock-based compensation expense related to performance based restricted stock awards.

A summary of the Company’s service-based restricted stock units during the three months ended March 31, 2024 is as follows:


Service Based Restricted Stock Units	Number of Shares	Weighted Average Grant-Date Fair Value
Unvested at January 1, 2024	258,885	$	1.83
Granted	249,990	1.39
Vested	(67,657)	1.37

Unvested at March 31, 2024	441,218	$	1.65

The fair value of service based restricted stock units are measured based on their fair value on the date of grant and amortized over the vesting period. The vesting periods range from 1 to 3 years. As of March 31, 2024, the unrecognized stock-based compensation expense was $0.4 million, which is expected to be recognized over the next 2.5 years.

The fair value of the service-based stock option awards granted for the three months ended March 31, 2024 were based on the following assumptions:


	Three Months Ended March 31, 2024	Three Months Ended March 31, 2023
Exercise price	$1.39	N/A
Expected stock price volatility	81.8%	N/A
Risk-free interest rate	4.31%	N/A
Term (years)	5.61 - 5.62	N/A

A summary of the Company’s service-based stock option activity for the three months ended March 31, 2024 is as follows:


Service Based Stock Option Awards	Shares Underlying Options	Weighted Average Exercise Price		Weighted Average Remaining Contractual Term	Aggregate Intrinsic Value (in $1,000's)
Outstanding at January 1, 2024	1,328,621	$	5.22
Granted	549,160	1.39

Forfeited	(1,750)	2.06

Outstanding at March 31, 2024	1,876,031	$	4.10	8.7	$	380,399

Exercisable at March 31, 2024	430,662	$	12.14	7.4	$	57,960

The aggregate intrinsic value is calculated as the difference between the closing price of the Company's common stock and the exercise price of the stock options that had strike prices below the closing price.

The weighted average grant date fair value for service based stock option awards granted during the three months ended March 31, 2024 was $0.98. No service based stock option awards were granted during the three months ended March 31, 2023.

As of March 31, 2024, total stock-based compensation expense related to unvested options not yet recognized totaled approximately $1.1 million, which is expected to be recognized over the next 3.3 years.