In October 2018, the Company’s Board of Directors approved a share repurchase plan (the “2018 Repurchase Plan”) authorizing the repurchase of $25.0 million worth of the Company’s common shares. During the nine months ended September 27, 2019, the Company repurchased 81 thousand shares for an aggregate purchase price of $6.7 million at an average price of $82.83 per share under the 2018 Repurchase Plan.

The table below summarizes share-based compensation expense recorded in the consolidated statements of operations (in thousands):

	Three Months Ended				Nine Months Ended
	September 27,		September 28,		September 27,		September 28,
	2019		2018		2019		2018
Selling, general and administrative	$	1,926	$	1,523	$	6,546	$	5,021
Research and development and engineering		171		114		466		306
Cost of revenue		146		58		336		148
Total share-based compensation expense	$	2,243	$	1,695	$	7,348	$	5,475

Share-based compensation reported in selling, general and administrative expenses included expenses related to restricted stock units and deferred stock units granted to the members of the Company’s Board of Directors of $0.9 million during the nine months ended September 27, 2019. Share-based compensation reported in selling, general and administrative expenses included expenses related to deferred stock units granted to the members of the Company’s Board of Directors of $0.5 million during the nine months ended September 28, 2018.

The Company’s restricted stock units (“RSUs”) have generally been issued with vesting periods ranging from zero to five years and vest based solely on service conditions. Accordingly, the Company recognizes compensation expense on a straight-line basis over the requisite service period. The Company reduces the compensation expense by an estimated forfeiture rate which is based on anticipated forfeitures and historical forfeiture experience.

Deferred stock units (“DSUs”) are granted to the members of the Company’s Board of Directors. Compensation expense associated with DSUs is recognized in full on the date of grant, as the DSUs are fully vested and non-forfeitable upon grant. There were 187 thousand and 179 thousand DSUs outstanding as of September 27, 2019 and December 31, 2018, respectively, which were included in the calculation of weighted average basic shares outstanding for the respective periods.

The table below summarizes activities relating to RSUs and DSUs issued and outstanding under the Company’s Amended and Restated 2010 Incentive Plan during the nine months ended September 27, 2019:

	Shares (In thousands)			Weighted Average Grant Date Fair Value
Unvested at December 31, 2018		529		$	26.98
Granted		111		$	75.93
Vested		(170	)	$	27.34
Forfeited		(23	)	$	48.01
Unvested at September 27, 2019		447		$	37.87
Expected to vest as of September 27, 2019		427

The total fair value of RSUs and DSUs that vested during the nine months ended September 27, 2019 was $13.2 million based on the market price of the underlying shares on the date of vesting.

The Company granted two types of performance-based stock awards to certain members of the executive management team: non-GAAP EPS performance-based restricted stock units (“EPS-PSUs”) and relative total shareholder return performance-based restricted stock units (“TSR-PSUs”). Both types of performance-based restricted stock units generally cliff vest on the first day following the end of the three-year performance period.

The number of common shares to be issued upon settlement following vesting of the EPS-PSUs is determined based on the Company’s cumulative non-GAAP EPS over a three-year performance period against the performance targets established by the Company’s Board of Directors at the time of grant and will be in the range of zero to 200% of the target number of shares. The Company recognizes compensation expense ratably over the performance period based on the number of shares that are deemed probable of vesting at the end of the three-year performance cycle. This probability assessment is performed quarterly and the cumulative effect of a change in the estimated compensation expense, if any, is recognized in the consolidated statement of operations in the period in which such determination is made.

The number of shares to be issued upon settlement following vesting of the TSR-PSUs is determined based on the relative market performance of the Company’s common shares compared to the Russell 2000 Index over a three-year performance period using a payout formula established by the Company’s Board of Directors at the time of grant and will be in the range of zero to 200% of the target number of shares. The Company recognizes the related compensation expense based on the fair value of the TSR-PSUs, determined using the Monte-Carlo valuation model as of the grant date, on a straight-line basis from the grant date to the end of the three-year performance period. Compensation expense will not be affected by the number of TSR-PSUs that will actually vest at the end of the three-year performance period.

The table below summarizes the activities relating to the performance-based awards issued and outstanding under the Company’s Amended and Restated 2010 Incentive Plan during the nine months ended September 27, 2019:

	Shares (In thousands)			Weighted Average Grant Date Fair Value
Unvested at December 31, 2018		137		$	37.28
Granted		46		$	92.63
Performance adjustment ⁽¹⁾		29		$	14.13
Vested		(59	)	$	14.13
Forfeited		—		$	—
Unvested at September 27, 2019		153		$	57.92
Expected to vest as of September 27, 2019		150

The total fair value of PSUs that vested during the nine months ended September 27, 2019 was $5.0 million based on the market price of the underlying shares on the date of vesting.

The fair value of the TSR-PSUs at the date of grant was estimated using the Monte-Carlo valuation model with the following assumptions:

	Nine Months Ended September 27, 2019
Grant-date stock price	$	77.23
Expected volatility		32.54	%
Risk-free interest rate		2.46	%
Expected annual dividend yield		—
Fair value	$	108.58

The fair value of stock options is estimated using the Black-Scholes valuation model. Key input assumptions include the expected option term, the expected volatility of the common shares over the expected term of the option, the risk-free interest rate, and the expected dividend yield. Compensation expense related to stock options is recognized in the consolidated statement of operations on a straight-line basis over the vesting period. No stock options were granted during the nine months ended September 27, 2019.

The total fair value of stock options that exercised during the nine months ended September 27, 2019, based on the difference between market price on the date of exercise and the date of grant, was $2.4 million. The total amount of cash received from the exercise of these stock options was $0.4 million. There were 73 thousand stock options outstanding as of September 27, 2019.