2. STOCK-BASED COMPENSATION

6 Months Ended

Nov. 30, 2014

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 and employee stock purchase plan, or ESPP, shares. Stock-based compensation cost is 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.  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 2014 filed on August 28, 2014 for further information regarding the stock option plan and the ESPP.

    The following table summarizes compensation costs related to the Company’s stock-based compensation for the three and six months ended November 30, 2014 and 2013 (in thousands):

	Three Months Ended				Six Months Ended
	November 30,				November 30,
	2014		2013		2014		2013
Stock-based compensation in the form of employee stock options and ESPP shares, included in:
Cost of sales	$	16	$	15	$	30	$	23
Selling, general and administrative		212		183		360		287
Research and development		49		49		84		80
Total stock-based compensation	$	277	$	247	$	474	$	390

     As of November 30, 2014, stock-based compensation costs of $60,000 were capitalized as part of inventory.  There were no stock-based compensation costs capitalized as part of inventory at November 30, 2013.

     During the three months ended November 30, 2014 and 2013, the Company recorded stock-based compensation related to stock options of $245,000 and $193,000, respectively.  During the six months ended November 30, 2014 and 2013, the Company recorded stock-based compensation related to stock options of $407,000 and $328,000, respectively.

     As of November 30, 2014, the total unrecognized stock-based compensation cost related to unvested stock-based awards under the Company’s 1996 Stock Option Plan and 2006 Equity Incentive Plan was approximately $1,749,000, which is net of estimated forfeitures of $4,000.  This cost will be amortized over the remaining service period of the underlying options.  The weighted average period is approximately 2.8 years.

     During the three months ended November 30, 2014 and 2013, the Company recorded stock-based compensation related to the ESPP of $32,000 and $54,000, respectively.  During the six months ended November 30, 2014 and 2013, the Company recorded stock-based compensation related to the ESPP of $67,000 and $62,000, respectively.

     As of November 30, 2014, the total compensation cost related to options to purchase the Company’s common stock under the ESPP but not yet recognized was approximately $148,000.  This cost will be amortized on a straight-line basis over a weighted average period of approximately 1.3 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 and six months ended November 30, 2014 and 2013 were estimated using the following weighted average assumptions in the Black-Scholes option valuation model:

	Three Months Ended						Six Months Ended
	November 30,						November 30,
	2014			2013			2014			2013
Expected term (in years)		4			4			4			4
Volatility		0.90			0.94			0.91			0.95
Expected dividend	$	0.00		$	0.00		$	0.00		$	0.00
Risk-free interest rates		1.11	%		0.95	%		1.25	%		1.40	%
Estimated forfeiture rate		0.25	%		0.25	%		0.25	%		0.25	%
Weighted average grant date fair value	$	1.32		$	1.77		$	1.64		$	1.03

     The fair values of the ESPP shares granted for the three and six months ended November 30, 2014 and 2013 were estimated using the following weighted-average assumptions:

	Three and Six Months Ended			Three and Six Months Ended
	November 30, 2014			November 30, 2013
Expected Term (in years)		0.5-2.0			0.5-2.0
Volatility		0.55-0.83			0.86-1.00
Expected Dividend	$	0.00		$	0.00
Risk-free Interest Rates		0.04%-0.53	%		0.04%-0.33	%
Estimated Forfeiture Rate		0	%		0	%
Weighted Average Grant Date Fair Value	$	1.47		$	1.34

     The following table summarizes the stock option transactions during the three and six months ended November 30, 2014 (in thousands, except per share data):

				Outstanding Options
							Weighted
				Number			Average		Aggregate
	Available			of			Exercise		Intrinsic
	Shares			Shares			Price		Value
Balances, May 31, 2014		1,145			3,002		$	1.31	$	2,913
Options granted		(625	)		625		$	2.65
Options terminated		9			(9	)	$	1.27
Options exercised		--			(295	)	$	1.07
Balances, August 31, 2014		529			3,323		$	1.59	$	3,277
Additional shares reserved		860			--
Options granted		(140	)		140		$	2.06
Options terminated		10			(10	)	$	1.74
Options exercised		--			(35	)	$	1.62
Balances, November 30, 2014		1,259			3,418		$	1.61	$	3,657
Options fully vested and expected to vest at November 30, 2014					3,350		$	1.61	$	3,584
Options exercisable at November 30, 2014					1,928		$	1.29	$	2,435

     The options outstanding and exercisable at November 30, 2014 were in the following exercise price ranges (in thousands, except per share data): 

	Options Outstanding						Options Exercisable
	at November 30, 2014						at November 30, 2014
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		680		4.34	$	0.70		561		4.39	$	0.72
$1.09-$1.40		1,327		4.47	$	1.28		737		4.06	$	1.28
$1.73-$2.06		547		3.58	$	1.92		372		2.21	$	1.91
$2.15-$2.71		864		6.18	$	2.63		258		4.99	$	1.68
$0.59-$2.71		3,418		4.74	$	1.61		1,928		3.92	$	1.29	$	2,435

     The total intrinsic value of options exercised during the three and six months ended November 30, 2014 was $29,000 and $435,000, respectively.  The total intrinsic value of options exercised during the three and six months ended November 30, 2013 was $110,000 and $153,000, respectively.  The weighted average remaining contractual life of the options exercisable and expected to be exercisable at November 30, 2014 was 4.74 years.