6. Stockholders’ Equity

Stock-Based Compensation

The fair value of the employee stock options granted during the period was estimated on the respective grant date using a Black-Scholes option-pricing model with the following weighted-average assumptions:

	Three Months Ended June 30,						Six Months Ended June 30,
	2017			2016			2017			2016
Expected term (in years)		6.0			5.8			6.0			5.7
Risk-free interest rate		2.0	%		1.2	%		2.1	%		1.2	%
Expected volatility		55	%		52	%		55	%		49	%
Expected dividend rate		—	%		—	%		—	%		—	%

Stock-based compensation expense, net of estimated forfeitures, was included in the following line items on the Condensed Consolidated Statements of Operations (in thousands):

	Three Months Ended June 30,				Six Months Ended June 30,
	2017		2016		2017		2016
Cost of revenue	$	41	$	101	$	106	$	306
Research and development		63		207		245		536
Sales and marketing		10		247		69		390
General and administrative		208		373		558		817
Total stock-based compensation	$	322	$	928	$	978	$	2,049

The following table presents stock-based compensation expense, net of estimated forfeitures, by grant type (in thousands):

	Three Months Ended June 30,				Six Months Ended June 30,
	2017		2016		2017		2016
Stock options	$	316	$	881	$	898	$	1,747
Restricted stock awards and restricted stock units (RSUs)		6		47		80		302
Total stock-based compensation	$	322	$	928	$	978	$	2,049

The following table presents unrecognized compensation expense, net of estimated forfeitures, related to the Company’s equity compensation plans as of June 30, 2017, which is expected to be recognized over the following weighted-average periods (in thousands, except for weighted-average period):

	Unrecognized		Weighted-
	Compensation		Average Period
	Expense		(in years)
Stock options	$	1,355		3.1
RSUs	$	310		2.7

The following table presents details on grants made by the Company for the following periods:

	Six Months Ended				Six Months Ended
	June 30, 2017				June 30, 2016
			Weighted-				Weighted-
			Average Grant				Average Grant
	Shares Granted		Date Fair Value		Shares Granted		Date Fair Value
Stock options		1,822,500	$	1.03		464,000	$	0.94
RSUs		300,000	$	0.96		—	$	—

The total intrinsic value of stock options exercised during the six months ended June 30, 2017 and 2016 was $0 million and $0.2 million, respectively.

RSUs that vested during the six months ended June 30, 2017 and 2016 had fair values of $0.1 million and $0.2 million, respectively, as of the vesting date.

Common Stock

As of June 30, 2017 and December 31, 2016, the Company had reserved shares of common stock for issuance as follows:

	As of June 30, 2017		As of December 31, 2016
Number of stock options outstanding		9,379,287		10,048,607
Number of RSUs outstanding		526,890		323,663
Shares available for future grant		7,811,415		5,163,386
Total shares reserved		17,717,592		15,535,656