STOCK-BASED COMPENSATION (Tables)

3 Months Ended

Aug. 31, 2022

STOCKBASED COMPENSATION

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

The following table summarizes the stock-based compensation expense for the three months ended August 31, 2022 and 2021 (in thousands):

	Three Months Ended
	August 31,
	2022		2021
Stock-based compensation in the form of stock options, RSUs and ESPP purchase rights, included in:
Cost of sales	$	91	$	82
Selling, general and administrative		465		395
Research and development		154		111
Total stock-based compensation	$	710	$	588

Fair value assumptions for Option Valuation Model

Fair Value. The fair value of the Company’s stock options granted to employees for the three months ended August 31, 2022 and 2021 were estimated using the following weighted average assumptions in the Black-Scholes option valuation model:

	Three Months Ended
	August 31,
	2022			2021
Expected term (in years)		5			6
Volatility		117	%		76	%
Risk-free interest rate		3.06	%		1.01	%
Weighted average grant date fair value	$	6.57		$	1.93

Stock option and RSU transactions

The following tables summarize the Company’s stock option and RSU transactions during the three months ended August 31, 2022 (in thousands):

	Available
	Shares
Balance, May 31, 2022		1,826
Options granted		(103	)
RSUs granted		(276	)
Options cancelled and adjusted		6
Balance, August 31, 2022		1,453

Stock option transactions

The following table summarizes the stock option transactions during the three months ended August 31, 2022 (in thousands, except per share data):

	Outstanding Options
				Weighted
	Number			Average		Aggregate
	of			Exercise		Intrinsic
	Shares			Price		Value
Balances, May 31, 2022		1,597		$	2.70	$	9,290
Options granted		103		$	8.00
Options cancelled		(6	)	$	2.41
Options exercised		(102	)	$	2.00
Balances, August 31, 2022		1,592		$	3.08	$	18,287
Options fully vested and expected to vest at August 31, 2022		1,569		$	3.08	$	18,030

Options outstanding

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

		Options Outstanding						Options Exercisable
		at August 31, 2022						at August 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		5.14	$	1.34		51		5.14	$	1.34
$1.64-$1.86			586		3.89	$	1.71		387		3.67	$	1.70
$2.03-$2.42			451		3.06	$	2.25		428		2.97	$	2.25
$2.76-$2.93			204		5.32	$	2.91		60		4.00	$	2.88
$3.46-$3.93			100		1.92	$	3.84		100		1.92	$	3.84
$8.00-$19.85			200		6.71	$	9.24		11		6.56	$	11.13
$1.34-$19.85			1,592		4.11	$	3.08		1,037		3.33	$	2.29	$	12,715