The 2016 Omnibus Incentive Plan (the “2016 Plan”) provides for grants of share‑based awards to employees, directors, and consultants. Awards may be in the form of stock options (“options”), tandem and non‑tandem stock appreciation rights, restricted share awards or restricted share units (“RSUs”), performance awards, and other share‑based awards. Forfeited or expired awards are returned to the incentive plan pool for future grants. Awards generally vest over four years, 25% on the first anniversary of the date of grant and quarterly thereafter over the remaining 3 years. Upon vesting of RSUs, employees may elect to have shares withheld to cover statutory minimum withholding taxes. Shares withheld are not reflected as an issuance of ordinary shares within our consolidated statements of shareholders’ equity, as the shares were never issued, and the associated tax payments are reflected as financing activities within our consolidated statements of cash flows.

Share‑based compensation expense across all plans for options, RSUs, and employee share purchase rights was $2.9 million and $1.3 million for the first quarter of 2020 and 2019, respectively.

	Number of Stock Options
	Time vesting			Performance vesting		Weighted average exercise price per share		Weighted average remaining contractual term	Aggregate intrinsic value (in thousands)
Outstanding, December 27, 2019		1,688,938			65,908	$	20.57
Granted		37,952			—	$	31.89
Exercised		(113,539	)		—	$	21.87
Forfeited or expired		—			—	$	—
Outstanding, March 27, 2020		1,613,351			65,908	$	20.74	4.5 years	$	3,803
Exercisable, March 27, 2020		697,920			65,908	$	17.49	3.2 years	$	3,604

	Number of Restricted Share Units
	Time vesting			Performance vesting		Weighted average grant date fair value per share
Unvested, December 27, 2019		389,170			17,730	$	23.03
Granted		78,479			—	$	32.08
Vested		(88,399	)		—	$	23.72
Forfeited		—			—	$	—
Unvested, March 27, 2020		379,250			17,730	$	24.67

The 2017 Employee Stock Purchase Plan (the “2017 ESPP”) grants employees the ability to designate a portion of their base-pay to purchase ordinary shares at a price equal to 85% of the fair market value of our ordinary shares on the first or last day of each 6 month purchase period. Purchase periods begin on January 1 or July 1 and end on June 30 or December 31, or the next business day if such date is not a business day. Shares are purchased on the last day of the purchase period.

During the first quarter of 2020, 16,520 ordinary shares were purchased by eligible employees under the 2017 ESPP. As of March 27, 2020, approximately 2.4 million ordinary shares remain available for purchase under the 2017 ESPP.