Under the 2017 Omnibus Incentive Plan (as amended from time to time, the Incentive Plan), the Company may grant awards of stock options, stock appreciation rights, restricted stock, restricted stock units, other stock-based awards and performance awards. As of June 30, 2022, the Company has 0.7 million shares of common stock available for issuance under the Incentive Plan, assuming the maximum potential number of shares that may be issued from outstanding awards.

Aggregate stock-based compensation charges, net of forfeitures, were $2.2 million and $0.8 million for the three months ended June 30, 2022 and 2021, respectively, and $6.4 million and $3.2 million for the six months ended June 30, 2022 and 2021, respectively. As of June 30, 2022, there was $1.2 million, $5.1 million, and $10.0 million of unrecognized stock-based compensation expense related to stock options, restricted stock units (RSUs) and performance stock units (PSUs) (both equity and liability awards), respectively. This expense will be recognized over the weighted average periods of 0.8 years for stock options, 1.6 years for RSUs and 1.3 years for PSUs.

During the six months ended June 30, 2022, there were 203,821 RSUs awarded to participants that are classified as equity. In addition, during the six months ended June 30, 2022, there were 235,393 PSUs awarded to participants that are classified as liabilities. During the six months ended June 30, 2022, there were no stock options granted.

The following table summarizes RSU grants under the Incentive Plan:


Grantee Type	# of RSUs Granted		Issued and Outstanding		Vesting Period	Weighted Average Grant Date Fair Value (Per Unit)
Director Group		830,978		71,771	1-2 years	$	11.21
Employee Group		2,393,066		656,392	3-5 years	$	9.36
Total				728,163

A summary of RSU awards activity under the Incentive Plan as of June 30, 2022, and the changes during the six months ended June 30, 2022 are as follows:


	Units			Weighted Average Grant Date Fair Value (Per Unit)
Non-vested as of January 1, 2022		673,830		$	8.56
Granted		203,821			12.16
Vested		(137,640	)		8.60
Forfeited		(11,848	)		9.76
Non-vested as of June 30, 2022		728,163		$	9.54

The weighted average grant date fair value of RSUs granted during the six months ended June 30, 2022 and 2021 was $12.16 and $6.92, respectively. The total fair value of RSUs vested during the six months ended June 30, 2022 and 2021 was $1.2 million and $1.4 million, respectively.

As of June 30, 2022, the Company had 3,100,571 PSUs outstanding, of which 1,355,571 were classified as liabilities.

As of June 30, 2022, there were 630,571 PSUs classified as liabilities in which the vesting occurs upon the achievement of specific performance-based conditions related to the Company’s financial performance over a three-year period, modified based on the Company’s Relative Total Shareholder Return (TSR) and subject to final vesting based on the participant’s continued employment through the end of the requisite service periods. The ultimate amount to vest may be downwardly adjusted by the Compensation Committee of the Company’s Board of Directors if the TSR is negative. The amount of awards that will ultimately vest for these PSUs can range from 0% to 200% based on the TSR calculated over a three-year period beginning January 1 of the year each grant was made. The Company currently expects that these PSUs will vest between 95% and 128%. The fair value of these PSUs will be remeasured at each period-end until the earlier of the date they are reclassified to equity or the vesting date. The inputs and assumptions used to calculate the fair value ranged from a remaining term of 1.50 to 2.50 years, risk-free interest rate of 2.11% to 2.39%, the expected volatility of 58.2% to 89.3%, and the expected dividend yield of 0.0%.

In addition, there are 725,000 PSUs classified as liabilities in which the vesting occurs upon the achievement of specific performance-based conditions related to the Company’s financial performance over a two-year period, subject to various subjective individual performance goals and subject to final vesting based on the participant’s continued employment through the end of the requisite service periods. The fair value of these PSUs will be remeasured at each period-end until the earlier of the date they are reclassified to equity or the vesting date. The Company currently expects that these PSUs will vest at 100%. The fair value is equal to the market value of the common stock at each period-end.

As of June 30, 2022, the total fair value of liability-classified awards was approximately $9.8 million, of which $3.3 million was recorded as a liability within other non-current liabilities on the consolidated balance sheet.