The table below sets forth information related to our share-based compensation expense:


	Three Months Ended
	March 31,
	2022		2021
Cost of goods sold	$	347	$	275
Selling, general and administrative		6,534		5,033
Research and development		1,021		814
Total share-based compensation expense	$	7,902	$	6,122

Share Grants – Share grants consist of restricted stock awards, restricted stock units and performance stock units ("PSUs"). Restricted stock awards and restricted stock units generally vest in equal annual installments over a four-year period and are measured based on the fair market value of the underlying stock on the date of grant. Compensation expense is recognized on a straight-line basis over the requisite four-year service period. All new grants are granted under the Company’s 2013 Equity Incentive Plan.

Performance stock units (“PSUs”) are measured based on the fair market value of the underlying stock on the date of grant, and compensation expense is recognized over the three-year performance period, with adjustments made to the expense to recognize the probable payout percentage.

As of March 31, 2022, total unrecognized share-based compensation expense related to share grants was approximately $69.7 million, before income taxes, and is expected to be recognized over a weighted average period of approximately 2.2 years.

Stock Options –We recognized stock option expense of less than $20 thousand for the three months ended March 31, 2022 and 2021, respectively. All stock option expense is related to stock options granted by Savitech Corporation (“Savitech”) in Savitech stock to their employees. We acquired a controlling interest in Savitech in 2020.