All share-based compensation is attributable to share grants. All outstanding stock options are fully vested, and all expense related to stock options has been recognized in previous periods. Approximately $2.0 million of cash proceeds were received from stock option exercises during the nine months ended September 30, 2020. The table below sets forth the line items where share-based compensation expense was recorded:

	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	2020		2019		2020		2019
Cost of goods sold	$	241	$	281	$	771	$	665
Selling, general and administrative		5,157		4,566		15,583		12,513
Research and development		892		742		2,330		2,186
Total share-based compensation expense	$	6,290	$	5,589	$	18,684	$	15,364

Share Grants – Restricted stock awards and restricted stock units generally vest in equal annual installments over a four-year period. All new grants are granted under the Company’s 2013 Equity Incentive Plan, and there will be no additional share grants under the 2001 Omnibus Equity Incentive Plan. Restricted stock grants are measured based on the fair market value of the underlying stock on the date of grant, and compensation expense is recognized on a straight-line basis over the requisite four-year service period. During the second quarter of 2020, in connection with the retirement of a member of the Company’s board of directors, the Company modified that director’s unvested RSU grants to vest upon his retirement. The shares subject to the modified grants will be released to that board member as if they were vesting under the original vesting timeline. In connection with this modification, the Company recorded additional expense of approximately $1.7 million.

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. PSUs will vest upon the Company achieving a cumulative 3-year non-GAAP operating income target for the applicable periods.

As of September 30, 2020, total unrecognized share-based compensation expense related to share grants was approximately $50.8 million, before income taxes, and is expected to be recognized over a weighted average period of approximately 2.2 years.