STOCKHOLDERS EQUITY AND STOCK-BASED COMPENSATION (Tables)

12 Months Ended

May 31, 2022

STOCKHOLDERS EQUITY AND STOCK-BASED COMPENSATION

Compensation costs related to the Company's stock-based compensation

The following table summarizes the stock-based compensation expense for the fiscal years ended May 31, 2022, 2021 and 2020 (in thousands, except per share data):

	Year Ended May 31,
	2022		2021		2020
Stock-based compensation in the form of stock options, RSUs, and ESPP purchase rights, included in:
Cost of sales	$	234	$	70	$	80
Selling, general and administrative		1,721		816		631
Research and development		968		215		199
Net effect on net income (loss)	$	2,923	$	1,101	$	910
Effect on net income (loss) per share:
Basic	$	0.11	$	0.05	$	0.04
Diluted	$	0.11	$	0.05	$	0.04

Fair value assumptions for Option Valuation Model

Fair Value. The fair values of the Company’s stock options granted to employees in fiscal 2022, 2021 and 2020 were estimated using the following weighted average assumptions in the Black-Scholes option valuation method:

	Year Ended May 31,
	2022			2021			2020
Expected term (in years)	5 - 6				6			5
Volatility		88.0	%		72.0	%		71.5	%
Risk-free interest rates		1.50	%		0.44	%		1.56	%
Weighted average grant date fair value	$	4.01		$	1.12		$	0.95

Fair value assumption of the ESPP Purchase Rights

The fair value of our ESPP purchase rights for the fiscal 2022, 2021 and 2020 was estimated using the following weighted average assumptions:

	Year End May 31,
	2022			2021			2020
Expected term (in years)	0.5 – 2.0			0.5 – 2.0			0.5 – 2.0
Volatility	101% – 272		%	74% – 88		%	62% – 77		%
Risk-free interest rates	0.05%–2.44		%	0.04%–0.17		%	0.14%–1.81		%
Weighted average grant date fair value	$	9.68		$	1.03		$	0.79

Stock option and RSU transactions

The following tables summarize the Company’s stock option and RSU transactions during fiscal 2022, 2021 and 2020 (in thousands):

	Available
	Shares
Balance, May 31, 2019		1,147
Additional shares reserved		1,196
Options granted		(738	)
RSUs granted		(25	)
Shares withheld for taxes and not issued		6
Options terminated		457
Options expired		(393	)
Balance, May 31, 2020		1,650
Options granted		(297	)
RSUs granted		(340	)
RSUs cancelled		1
Shares withheld for taxes and not issued		9
Options terminated		455
Options expired		(341	)
Balance, May 31, 2021		1,137
Additional shares reserved		1,414
Options granted		(303	)
RSUs granted		(522	)
RSUs cancelled		10
Shares withheld for taxes and not issued		(15	)
Options terminated		105
Balance, May 31, 2022		1,826

Stock option transactions

The following table summarized the stock option transactions during fiscal 2022, 2021 and 2020 (in thousands, except per share data):

	Outstanding Options
				Weighted
	Number			Average		Aggregate
	of			Exercise		Intrinsic
	Shares			Price		Value
Balances, May 31, 2019		3,107		$	2.20	$	283
Options granted		738		$	1.61
Options terminated		(457	)	$	1.98
Options exercised		(235	)	$	1.22
Balances, May 31, 2020		3,153		$	2.17	$	102
Options granted		297		$	1.78
Options terminated		(455	)	$	2.31
Options exercised		(229	)	$	1.54
Balances, May 31, 2021		2,766		$	2.16	$	807
Options granted		303		$	5.37
Options terminated		(105	)	$	1.59
Options exercised		(1,367	)	$	2.28
Balances, May 31, 2022		1,597		$	2.70	$	9,290
Options fully vested and expected to vest at May 31, 2022		1,570		$	2.69	$	9,138

Options outstanding

The options outstanding and exercisable at May 31, 2022 were in the following exercise price ranges (in thousands, except per share data):

		Options Outstanding						Options Exercisable
		at May 31, 2022						at May 31, 2022
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
$	1.34		51		5.39	$	1.34		51		5.39	$	1.34
$1.64-$1.86			659		4.02	$	1.70		419		3.71	$	1.69
$2.03-$2.42			471		3.33	$	2.25		408		3.21	$	2.26
$2.76-$2.93			215		5.60	$	2.91		56		4.12	$	2.87
$3.46-$3.93			104		2.17	$	3.84		104		2.17	$	3.84
$9.45-$19.85			97		6.80	$	10.57		4		6.64	$	14.02
$1.34-$19.85			1,597		4.12	$	2.70		1,042		3.47	$	2.22	$	6,440