Restricted Stock Units (“RSUs”) and Restricted Stock. RSUs represent the right to receive unrestricted shares of the Company’s common stock at the time of vesting, subject to any restrictions as specified in the individual holder’s award agreement. RSUs are subject to graded vesting, generally ranging between one and four years and the fair value of the RSUs is equal to the Company's common stock price on the date of grant. Restricted Stock represents RSUs that have been delivered to certain non-employee directors who have elected to receive shares underlying RSUs before they vest. Restricted Stock is subject to graded vesting over one year and the fair value of the Restricted Stock is equal to the Company’s common stock price on the date of grant. RSU and Restricted Stock activity for the six months ended June 30, 2021 is as follows (in thousands, except for weighted-average grant date fair value):


	Number of RSUs and Restricted Stock			Weighted-Average Grant Date Fair Value
Outstanding as of December 31, 2020		4,061		$	8.31
Granted		1,554			15.02
Vested and delivered		(1,493	)		8.36
Forfeited		(201	)		9.13
Outstanding as of June 30, 2021 (1)		3,921			10.91

(1)

Included in “Outstanding as of June 30, 2021” are 64 RSUs that were vested, but not yet delivered.

Performance Stock Units (“PSUs”). PSUs represent the right to receive unrestricted shares of the Company’s common stock at the time of vesting. The fair value of the PSUs is equal to the Company’s common stock price on the date of grant. Expense related to PSUs is recognized when the performance conditions are probable of being achieved. The percentage of PSUs that shall vest will range from 0% to 200% of the number of PSUs granted based on the Company’s future performance related to certain revenue and adjusted earnings before interest, income taxes, depreciation and amortization targets over a three-year performance period. These PSUs are subject to cliff vesting at the end of the respective performance period. PSU activity for the six months ended June 30, 2021 is as follows (in thousands, except for weighted-average grant date fair value):


	Number of PSUs			Weighted-Average Grant Date Fair Value
Outstanding as of December 31, 2020		730		$	9.28
Granted		—			—
Vested and delivered		(588	)		5.74
Forfeited		—			—
Outstanding as of June 30, 2021		142			23.98

Stock Options. Stock options represent the right to purchase shares of the Company’s common stock at the time of vesting, subject to any restrictions as specified in the individual holder’s award agreement. Stock options are subject to three-year cliff vesting and expire

10 years from the grant date. Stock option activity for the six months ended June 30, 2021 is as follows (in thousands, except for weighted-average grant date fair value and weighted-average remaining contractual term):


	Number of Options		Weighted-Average Grant Date Fair Value		Weighted-Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value
Outstanding as of December 31, 2020		513	$	2.80		9.22	$	3,028
Granted		291		9.63		—		—
Exercised		—		—		—		—
Forfeited		—		—		—		—
Outstanding as of June 30, 2021		804		5.27		9.08		4,583
Exercisable as of June 30, 2021		—		—		—		—

The fair value of the stock options granted during the six months ended June 30, 2021 and 2020 are estimated on the grant date using the Black-Scholes option pricing model, using the following assumptions:


	2021			2020
Risk-free interest rate		1.15	%		1.01	%
Weighted-average volatility		69.00	%		53.08	%
Dividend yield		0	%		0	%
Expected years until exercise		6.5			6.5