The Company grants options and RSUs under the 2016 Incentive Plan (the "2016 Plan"), under which awards may be granted to all employees. Award vesting periods for this plan are generally four years. In May 2020, the Company adopted amendments to the 2016 Plan which increased the number of shares of the Company’s common stock that may be issued under the 2016 plan by an additional 2.0 million shares. In addition, any shares subject to restricted stock, restricted stock units, performance units, or performance shares granted on or after May 28, 2020 under the 2016 Plan will be counted against the shares available for issuance as one share for every one share subject to such awards. As of June 28, 2020, approximately 2.7 million shares were reserved for future grants under the 2016 Plan.

Additionally, the Company sponsors an Employee Stock Purchase Plan (the “ESPP”), pursuant to which eligible employees may contribute up to 10% of compensation, subject to certain income limits, to purchase shares of the Company’s common stock. The terms of the plan include a look-back feature that enables employees to purchase stock at a price equal to 85% of the lesser of the fair market value at the beginning of the offering period or the purchase date. The duration of each offering period is generally six-months. As of June 28, 2020, approximately 0.5 million shares were available for issuance under the ESPP.

	Number of Shares			Weighted Average Exercise Price Per Share
	(In thousands)			(In dollars)
Outstanding as of December 31, 2019		2,188		$	26.03
Exercised		(190	)	$	20.00
Cancelled		(20	)	$	35.85
Expired		(3	)	$	22.06
Outstanding as of June 28, 2020		1,975		$	26.51

	Number of Shares			Weighted Average Grant Date Fair Value Per Share
	(In thousands)			(In dollars)
Outstanding as of December 31, 2019		1,587		$	33.95
Granted		682		$	24.98
Vested		(486	)	$	33.11
Cancelled		(53	)	$	36.25
Outstanding as of June 28, 2020		1,730		$	30.58

The Company measures stock-based compensation at the grant date based on the estimated fair value of the award. Estimated compensation cost relating to RSUs is based on the closing fair market value of the Company’s common stock on the date of grant. The fair value of options granted and the purchase rights granted under the ESPP is estimated on the date of grant using a Black-Scholes-Merton option valuation model that uses the assumptions noted in the following table. The estimated expected term of options granted is derived from historical data on employee exercise and post-vesting employment termination behavior. The risk-free interest rate of options granted and the purchase rights granted under the ESPP is based on the implied yield currently available on U.S. Treasury securities with a remaining term commensurate with the estimated expected term. Expected volatility of options granted under the 2016 Plan and the purchase rights granted under the ESPP is based on historical volatility over the most recent period commensurate with the estimated expected term.

No options were granted during the three or six months ended June 28, 2020 and June 30, 2019 and no purchase rights were granted during the three months ended June 28, 2020 and June 30, 2019. The following table sets forth the weighted average assumptions used to estimate the fair value of purchase rights granted under the ESPP during the six months ended June 28, 2020 and June 30, 2019:

	Six Months Ended
	June 28, 2020			June 30, 2019
	ESPP
Expected life (in years)		0.5			0.5
Risk-free interest rate		1.55	%		2.49	%
Expected volatility		38.8	%		42.6	%
Dividend yield		—			—

The following table sets forth the stock-based compensation expense resulting from stock options, RSUs and the ESPP included in the Company’s unaudited condensed consolidated statements of operations:

	Three Months Ended				Six Months Ended
	June 28, 2020		June 30, 2019		June 28, 2020		June 30, 2019
	(In thousands)
Cost of revenue	$	1,501	$	755	$	2,206	$	1,423
Research and development		1,707		1,288		2,741		2,480
Sales and marketing		1,890		2,085		3,669		4,126
General and administrative		4,074		2,611		6,892		5,168
Total	$	9,172	$	6,739	$	15,508	$	13,197

As of June 28, 2020, $5.2 million of unrecognized compensation cost related to stock options is expected to be recognized over a weighted-average period of 1.6 years. $44.6 million of unrecognized compensation cost related to unvested RSUs is expected to be recognized over a weighted-average period of 2.4 years.