2. STOCK-BASED COMPENSATION

3 Months Ended

Aug. 31, 2016

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

2. STOCK-BASED COMPENSATION

2. STOCK-BASED COMPENSATION

    Stock-based compensation expense consists of expenses for stock options, restricted stock units, or RSUs, and employee stock purchase plan, or ESPP, purchase rights. Stock-based compensation cost for stock options and ESPP purchase rights are measured at each grant date, based on the fair value of the award using the Black-Scholes option valuation model, and is recognized as expense over the employee’s requisite service period. This model was developed for use in estimating the value of publicly traded options that have no vesting restrictions and are fully transferable. The Company’s employee stock options have characteristics significantly different from those of publicly traded options. For RSUs, stock-based compensation cost is based on the fair value of the Company’s common stock at the grant date. All of the Company’s stock-based compensation is accounted for as an equity instrument. See Notes 10 and 11 in the Company’s Annual Report on Form 10-K for fiscal 2016 filed on August 29, 2016 for further information regarding the stock option plan and the ESPP.

    The following table summarizes the stock-based compensation expense related to the Company’s stock-based incentive plans for the three months ended August 31, 2016 and 2015 (in thousands):

	Three Months Ended
	August 31,
	2016		2015
Stock-based compensation in the form of employee stock options, RSUs and ESPP purchase rights, included in:
Cost of sales	$	24	$	22
Selling, general and administrative		247		238
Research and development		48		59
Total stock-based compensation	$	319	$	319

    As of August 31, 2016 and 2015, there were no stock-based compensation costs capitalized as part of inventory.

    During the three months ended August 31, 2016 and 2015, the Company recorded stock-based compensation related to stock options and RSUs of $279,000 and $286,000, respectively.

    As of August 31, 2016, the total compensation cost related to unvested stock-based awards under the Company’s 1996 Stock Option Plan and 2006 Equity Incentive Plan, but not yet recognized, was approximately $1,258,000, which is net of estimated forfeitures of $3,000. This cost will be amortized on a straight-line basis over a weighted average period of approximately 2.5 years.

    During the three months ended August 31, 2016 and 2015, the Company recorded stock-based compensation related to the ESPP of $40,000 and $33,000, respectively.

    As of August 31, 2016, the total compensation cost related to purchase rights under the ESPP but not yet recognized was approximately $98,000. This cost will be amortized on a straight-line basis over a weighted average period of approximately 1.1 years.

Valuation Assumptions

    Valuation and Amortization Method. The Company estimates the fair value of stock options granted using the Black-Scholes option valuation model and a single option award approach. The fair value under the single option approach is amortized on a straight-line basis over the requisite service periods of the awards, which is generally the vesting period.

    Expected Term. The Company’s expected term represents the period that the Company’s stock-based awards are expected to be outstanding and was determined based on historical experience, giving consideration to the contractual terms of the stock-based awards, vesting schedules and expectations of future employee behavior as evidenced by changes to the terms of its stock-based awards.

    Expected Volatility. Volatility is a measure of the amounts by which a financial variable such as stock price has fluctuated (historical volatility) or is expected to fluctuate (expected volatility) during a period. The Company uses the historical volatility for the past four or five years, which matches the expected term of most of the option grants, to estimate expected volatility. Volatility for each of the ESPP’s four time periods of six months, twelve months, eighteen months, and twenty-four months is calculated separately and included in the overall stock-based compensation cost recorded.

    Dividends. The Company has never paid any cash dividends on its common stock and does not anticipate paying any cash dividends in the foreseeable future. Consequently, the Company uses an expected dividend yield of zero in the Black-Scholes option valuation model.

    Risk-Free Interest Rate. The Company bases the risk-free interest rate used in the Black-Scholes option valuation model on the implied yield in effect at the time of option grant on U.S. Treasury zero-coupon issues with a remaining term equivalent to the expected term of the stock awards including the ESPP.

    Estimated Forfeitures. When estimating forfeitures, the Company considers voluntary termination behavior as well as analysis of actual option forfeitures.

    Fair Value. The fair value of the Company’s stock options granted to employees for the three months ended August 31, 2016 were estimated using the following weighted average assumptions in the Black-Scholes option valuation model:

	August 31,
	2016
Expected term (in years)		4
Volatility		0.82
Expected dividend	$	0.00
Risk-free interest rate		1.01	%
Weighted average grant date fair value	$	1.00

    There were no stock options granted to employees for the three months ended August 31, 2015.

    During the three months ended August 31, 2016, RSUs were granted for 138,000 shares. The market value on the date of the grant was $1.68 per share.

    There were no ESPP purchase rights granted to employees for the three months ended August 31, 2016 and 2015.

           The following tables summarize the Company’s stock option and RSU transactions during three months ended August 31, 2016 (in thousands):

	Available
	Shares
Balance, May 31, 2016		1,847
Options granted		(318	)
RSUs granted		(138	)
Shares cancelled		46
Balance, August 31, 2016		1,437

  The following table summarizes the stock option transactions during the three months ended August 31, 2016 (in thousands, except per share data):

	Outstanding Options
		Number of Shares			Weighted Average Exercise Price		Aggregate Intrinsic Value
Balances, May 31, 2016		3,201		$	1.66	$	189
Options granted		318		$	1.68
Options cancelled		(46	)	$	1.40
Options exercised		(91	)	$	1.32
Balances, August 31, 2016		3,382		$	1.67	$	2,694
Options fully vested and expected to vest at August 31, 2016		3,314		$	1.67	$	2,640
Options exercisable at August 31, 2016		2,379		$	1.52	$	2,235

    The options outstanding and exercisable at August 31, 2016 were in the following exercise price ranges (in thousands, except per share data):

		Options Outstanding						Options Exercisable
		at August 31, 2016						at August 31, 2016
	Range of Exercise Prices		Number Outstanding Shares		Weighted Average Remaining Contractual Life (Years)	Weighted Average Exercise Price		Number Exercisable Shares		Weighted Average Remaining Contractual Life (Years)			Weighted Average Exercise Price		Aggregate Intrinsic Value
$	0.59-$0.97			565	2.57	$	0.68		565		2.57	$	0.68
$	1.09-$1.40			1,039	3.03	$	1.28		923		2.91	$	1.28
$	1.68-$2.06			548	5.88	$	1.77		215		4.60	$	1.90
$	2.10-$2.71			1,230	5.20	$	2.43		676		5.12	$	2.45
$	0.59-$2.71			3,382	4.21	$	1.67		2,379		3.61	$	1.52	$	2,235

    The total intrinsic value of options exercised during the three months ended August 31, 2016 was $52,000. The total intrinsic value of options exercised during the three months ended August 31, 2015 was $60,000. The weighted average remaining contractual life of the options exercisable and expected to be exercisable at August 31, 2016 was 4.21 years.