NOTE 8—STOCK-BASED COMPENSATION

As of June 30, 2018, 4,374,461 shares of common stock were available for grant under the Company’s 2016 Equity Incentive Plan.

The following table summarizes the Company’s stock option activities for the three months ended June 30, 2018:


			Weighted
		Number of Shares	Average	Weighted
	Shares	Underlying	Remaining	Average
	Available for	Options	Contractual	Exercise		Intrinsic
	Grant	Outstanding	Life (Years)	Price		Value
Balance at March 31, 2018	4,444,301	7,874,267		$	5.45
Granted	(78,590)	78,590		$	7.70
Exercised	—	(300,528)		$	3.92	$	1,054,096
Forfeited	8,750	(38,550)		$	4.57
Balance at June 30, 2018	4,374,461	7,613,779	5.53	$	5.53
Options vested and exercisable		5,046,534	4.08	$	5.34	$	11,189,643
Options vested and expected to vest		7,556,754	5.51	$	5.53	$	15,312,078

The weighted average fair value per underlying share of options granted during the three months ended June 30, 2018 and 2017 was $2.76 and $2.58, respectively.

Options outstanding by exercise price at June 30, 2018 were as follows:


				Number of	Options Outstanding			Options Exercisable
				Shares	Weighted		Weighted Average		Weighted
				Underlying	Average		Remaining	Number	Average
				Options	Exercise		Contractual	Vested and	Exercise
Exercise Price				Outstanding	Price		Life (Years)	Exercisable	Price
$	2.43	-	3.60	794,891	$	3.36	3.99	608,537	$	3.33
$	3.75	-	4.34	828,326	$	4.09	2.67	792,876	$	4.08
$	4.43	-	4.98	1,052,821	$	4.88	5.37	629,617	$	4.83
$	4.99	-	5.23	1,157,976	$	5.10	7.21	637,576	$	5.18
$	5.28	-	5.76	762,790	$	5.55	5.98	619,466	$	5.61
$	6.00	-	6.45	777,918	$	6.19	5.00	550,685	$	6.20
$	6.54	-	6.86	1,114,076	$	6.74	5.21	874,185	$	6.70
$	7.00	-	7.40	812,001	$	7.22	7.67	225,012	$	7.09
$	7.70	-	8.09	204,400	$	7.95	9.68	-	$	-
$	9.20			108,580	$	9.20	2.59	108,580	$	9.20
				7,613,779	$	5.53	5.53	5,046,534	$	5.34

The following table summarizes stock-based compensation expense by line item in the Condensed Consolidated Statements of Operations, all relating to employee stock plans:


	Three Months Ended June 30,
	2018		2017
	(In thousands)
Cost of revenues	$	53	$	47
Research and development		323		267
Selling, general and administrative		166		164
Total	$	542	$	478

As stock-based compensation expense recognized in the Condensed Consolidated Statement of Operations is based on awards ultimately expected to vest, it has been reduced for estimated forfeitures in accordance with authoritative guidance. The Company estimates forfeitures at the time of grant and revises the original estimates, if necessary, in subsequent periods if actual forfeitures differ from those estimates.

No tax benefit related to stock-based compensation was recognized in the three months ended June 30, 2018 due to a full valuation allowance. There were no windfall tax benefits realized from exercised stock options in either of these periods. Compensation cost capitalized within inventory at June 30, 2018 was immaterial. As of June 30, 2018, the Company’s total unrecognized compensation cost was $3.8 million, which will be recognized over a weighted average period of 2.11 years. The Company calculated the fair value of stock-based awards in the periods presented using the Black-Scholes option pricing model and the following weighted average assumptions:


	Three Months Ended June 30,
	2018			2017
	(In thousands)
Stock Option Plans:
Risk-free interest rate		2.78	%		1.91	%
Expected life (in years)		5.00			5.00
Volatility		35.6	%		36.5	%
Dividend yield		—	%		—	%
Employee Stock Purchase Plan:
Risk-free interest rate		2.09	%		1.04	%
Expected life (in years)		0.50			0.50
Volatility		37.7	%		51.1	%
Dividend yield		—	%		—	%