We have awarded stock options to certain employees and certain non-employee members on our Board of Directors. The grants generally vest over a four-year period. The fair value of stock options is determined using the Black-Scholes option pricing model. There were no stock options granted during the 13 weeks ended March 28, 2021.

A summary of stock option activity for the 13 weeks ended March 28, 2021 is as follows:

Options	Shares (Thousands)			Weighted Average Exercise Price		Aggregate Intrinsic Value (Thousands)		Weighted Average Remaining Term (Years)
Outstanding—December 27, 2020		1,233		$	10.68	$	—		2.49
Granted		—			—
Exercised		—			—
Canceled		(307	)		12.61
Outstanding—March 28, 2021		926			10.04	$	—		1.81
Exercisable—March 28, 2021		922		$	10.03	$	—		1.79

Stock-based compensation related to stock options is measured at the grant date based on the calculated fair value of the award, and is recognized as expense over the requisite employee service period, which is generally the vesting period of the grant with a corresponding increase to additional paid-in capital. For the 13 weeks ended March 28, 2021, we recognized stock-based compensation expense related to stock options of $0.1 million. For the 13 weeks ended March 29, 2020, we recognized stock-based compensation expense related to stock options of $0.2 million. As of March 28, 2021, unrecognized stock-based compensation expense for stock options was $0.1 million, which will be recognized through fiscal year 2022. We record stock-based compensation expense within general and administrative expenses in the condensed consolidated statements of operations.

We award restricted stock units (“RSUs”) to certain employees and certain non-employee members on our Board of Directors. The Board of Director grants have a vesting schedule of 50% on the first anniversary of the grant date and 50% on the second anniversary of the grant date. The employee grants vest in one-third increments over a three-year period. For the 13 weeks ended March 28, 2021, we recognized stock-based compensation expense related to RSUs of $0.1 million. For the 13 weeks ended March 29, 2020, we recognized stock-based compensation expense related to RSUs of $0.3 million. As of March 28, 2021, unrecognized stock-based compensation expense for RSUs was $1.9 million, which will be recognized though fiscal year 2023.

RSUs	Number of RSUs (Thousands)			Weighted Average Fair Value per Share
Non-vested as of December 27, 2020		994		$	3.35
Granted		179			5.60
Vested		(22	)		6.02
Canceled		(13	)		—
Non-vested as of March 28, 2021		1,138		$	3.59

We award performance share units (“PSUs”) to certain of its employees. The PSUs have certain vesting conditions based upon our financial performance or our stock price.

We have granted PSUs that are subject to service and market vesting conditions. The fair market value was established using a Monte Carlo simulation model. Participants are entitled to receive a specified number of shares of our common stock contingent on achievement of a stock return on our common stock. The PSUs may vest during a performance period of five years. Compensation expense for these awards is being amortized over an average expected service period or earlier based on when each tranche’s vesting conditions are met. For the 13 weeks ended March 28, 2021, we recognized stock-based compensation expense for PSUs with market vesting conditions of $0.1 million.

A summary of activity for PSUs with market vesting conditions for the 13 weeks ended March 28, 2021 is as follows:

PSUs	Number of PSUs (Thousands)			Weighted Average Fair Value per Share
Non-vested as of December 27, 2020		502			1.38
Granted		—			—
Vested		(41	)		5.66
Canceled		—			—
Non-vested as of March 28, 2021		461		$	1.37