Share-based grants are designed to reward employees for their long-term contributions to us and provide incentives for them to remain with us.

As of June 30, 2020, options to purchase 1,684,718 shares of Class B common stock were outstanding with a weighted average exercise price of $24.80 per share.

As of June 30, 2020, options to purchase 9,510,910 shares of Class B common stock were outstanding with a weighted average exercise price of $27.15 per share and no shares were available for future grant. As of June 30, 2020, we had outstanding RSUs that may be settled for 4,019,194 shares of Class B common stock under the plan.

As of June 30, 2020, options to purchase 5,975,977 shares of Class A common stock were outstanding with a weighted average exercise price of $9.25 per share and 3,688,910 shares of outstanding RSUs that may be settled for Class A common stock which were granted pursuant to the plan.

We used the following weighted-average assumptions in applying the Black-Scholes valuation model for determination of options:


	Three Months Ended June 30,			Six Months Ended June 30,
	2020	2019	2020	2019

Risk-free interest rate	0.6%	2.4%- 2.5%	0.6%	2.4% - 2.6%
Expected term (years)	6.6	6.4 - 6.7	6.6	6.4 - 6.7
Expected dividend yield	—	—	—	—
Expected volatility	71.0%	47.5%	71.0%	47.5% - 50.2%

The following table summarizes the components of stock-based compensation expense in the condensed consolidated statements of operations (in thousands):


	Three Months Ended June 30,						Six Months Ended June 30,
	2020		2019		2020		2019
			As Restated				As Restated

Cost of revenue	$	4,736	$	10,538	$	10,243	$	28,850
Research and development	4,714		12,218		10,810		26,448
Sales and marketing	2,234		8,935		6,124		20,447
General and administrative	6,947		19,673		14,473		43,441
	$	18,631	$	51,364	$	41,650	$	119,186

Stock-based Compensation - During the three months ended June 30, 2020 and 2019, we recognized $18.6 million and $51.4 million of total stock-based compensation costs, respectively. During the six months ended June 30, 2020 and 2019, we recognized $41.7 million and $119.2 million of total stock-based compensation costs, respectively.

During the three months ended June 30, 2020 and 2019, we recognized $0.9 million and $6.2 million, respectively, of stock-based compensation expense previously capitalized in inventory and property, plant and equipment. During the six months ended June 30, 2020 and 2019, we recognized $1.8 million and $17.0 million, respectively, of stock-based compensation expense previously capitalized in inventory and property, plant and equipment.


	Outstanding Options
	Number of Shares	Weighted Average Exercise Price		Remaining Contractual Life (Years)	Aggregate Intrinsic Value

					(in thousands)




December 31, 2019	17,837,316	$	20.76	6.94	$	14,964
Granted	200,000	7.30
Exercised	(170,873)	5.90
Cancelled	(694,838)	22.46
Balances at June 30, 2020	17,171,605	20.69		6.46	26,824
Vested and expected to vest at Current period end	16,555,245	21.08		6.37	24,325
Exercisable at Current period end	9,515,698	28.48		4.67	384

Stock Options - During the three months ended June 30, 2020 and 2019, we recognized $4.9 million and $9.0 million of stock-based compensation costs for stock options, respectively. During the six months ended June 30, 2020 and 2019, we recognized $10.5 million and $18.2 million of stock-based compensation costs for stock options, respectively.

We granted 200,000 options of Class A common stock during the three and six months ended June 30, 2020 and the weighted average grant-date fair value of those options was $7.30 per share.

As of June 30, 2020 and 2019, we had unrecognized compensation costs related to unvested stock options of $31.0 million and $56.8 million, respectively. This cost is expected to be recognized over the remaining weighted-average period of 2.2 years and 2.6 years, respectively. We had no excess tax benefits in the quarters ended June 30, 2020 and 2019. Cash received from stock options exercised totaled $1.0 million and $ 1.4 million ended June 30, 2020 and 2019, respectively.


	Number of Awards Outstanding	Weighted Average Grant Date Fair Value





Unvested Balance at December 31, 2019	10,112,266	$	17.29
Granted	1,214,942	8.75
Vested	(3,320,153)	19.06
Forfeited	(298,951)	15.50
Balances at June 30, 2020	7,708,104	15.26

Restricted Stock Units - The estimated fair value of RSU awards is based on the fair value of our Class A common stock on the date of grant. For the three months ended June 30, 2020 and June 30, 2019, we recognized $10.5 million and $39.7 million of stock-based compensation costs for RSUs, respectively. For the six months ended June 30, 2020 and June 30, 2019, we recognized $23.7 million and $90.7 million of stock-based compensation costs for RSUs, respectively.

As of June 30, 2020, we had $35.3 million of unrecognized stock-based compensation cost related to unvested RSUs. This cost is expected to be recognized over a weighted average period of 1.2 years. As of June 30, 2019, we had $108.2 million of unrecognized stock-based compensation cost related to unvested RSUs. This expense was expected to be recognized over a weighted average period of 1.1 years.

The following table presents the stock activity and the total number of RSUs available for grant under our stock plans as of June 30, 2020:


						Plan Shares Available for Grant







Balances at December 31, 2019						17,233,144
Added to plan						6,654,552
Granted						(1,414,942)

Cancelled						992,262
Expired						(675,276)
Balances at June 30, 2020						22,789,740

During the three months ended June 30, 2020 and 2019, we recognized $1.8 million and $2.4 million of stock-based compensation costs under our 2018 Employee Stock Purchase Plan (the "2018 ESPP"), respectively. During the six months ended June 30, 2020 and 2019, we recognized $4.7 million and $5.2 million of stock-based compensation costs for the 2018 ESPP, respectively. We issued 992,846 shares in the six months ended June 30, 2020. During the first six months of 2020, we added an additional 1,494,819 shares and there were 3,532,380 shares available for issuance as of June 30, 2020.

In November 2019, the Board approved stock options ("2019 Executive Awards") to certain executive staff. The 2019 Executive Awards consist of three vesting tranches with a vesting schedule based on the attainment of market conditions and assuming continued employment and service through each vesting date. Stock-based compensation costs associated with the 2019 Executive Awards are recognized over the service period, even though no tranches of the 2019 Performance Awards vest unless a market condition is achieved. The grant date fair value of the options is determined using a Monte Carlo simulation.

In June 2020, the Board approved stock awards ("2020 Executive Awards") to certain executive staff. The 2020 Executive Awards consist of three vesting tranches with an annual vesting schedule based on the attainment of performance conditions and assuming continued employment and service through each vesting date. Stock-based compensation costs associated with the 2020 Executive Awards is recognized over the service period as we evaluate the probability of the achievement of the performance conditions.