Our 2018 Equity Incentive Plan (the “Plan”) was approved by stockholders in May 2018, authorizing us to issue up to 4.35 million shares of common stock, along with non-qualified stock options, stock appreciation rights, restricted stock units and performance restricted stock units to our officers, key employees, non-employee directors and consultants. In May 2021, the stockholders approved an amendment to the Plan that, among other things, increased the authorized shares by 2 million. At March 31, 2022, there were 0.3 million shares available for future grants under this Plan. It is our policy to issue shares from authorized but not issued shares upon the exercise of stock options.

Under the terms of the Plan, each year eligible participants are granted time value restricted stock units (“RSUs”), vesting ratably over a three-year period, and performance restricted stock units (“PSUs”), with a three-year cliff vesting. Upon vesting, each restricted stock award is exchangeable for one share of the Company’s common stock, with accrued dividends.

RSU, PSU and option activity for the three months ended March 31, 2022 is summarized in the following table:

	Equity Incentive Awards
	Restricted Stock Units			Weighted Average Grant Date Fair Value		Performance Shares			Weighted Average Grant Date Fair Value		Options		Weighted Average Exercise Price
Balance at December 31, 2021		966,429		$	4.62		2,484,581		$	6.67		9,000	$	16.76
Granted		333,673			4.28		667,345			5.33		—		—
Settled		(381,743	)		4.02		(719,659	)		6.68		—		—
Forfeited or expired		(4,570	)		3.77		(109,166	)		7.24		—		—
Balance at March 31, 2022		913,789		$	4.75		2,323,101		$	6.26		9,000	$	16.76

Awards estimated to vest in the future		897,734		$	4.79		2,056,141		$	6.31		9,000	$	16.76

Stock-based compensation expense for the three months ended March 31, 2022 and 2021 was $2.6 million and $1.8 million, respectively.Unrecognized stock-based compensation expense related to non-vested awards of $12.2 million is expected to be recognized over a weighted average period of approximately 2.1 years as of March 31, 2022.