Stock-Based Compensation

The Company accounts for its stock-based compensation at fair value. The following table summarizes stock-based compensation expense by financial statement line item for the

three

and

nine

months ended

December 31, 2020

and

2019

(in thousands):

	Three Months Ended December 31,					Nine Months Ended December 31,
	2020			2019		2020		2019
Cost of revenues	$	(23	)	$	21	$	35	$	45
Research and development		179			117		470		219
Selling, general and administrative		683			452		2,092		971
Total	$	839		$	590	$	2,597	$	1,236

The Company issued

27,341

shares of immediately vested common stock and

697,167

shares of restricted stock awards during the

nine

months ended

December 31, 2020

and issued

13,174

shares of immediately vested common stock and

366,000

shares of restricted stock awards during the

nine

months ended

December 31, 2019

. These restricted stock awards generally vest over

years. Awards for restricted stock include both time-based and performance-based awards. For options and restricted stock awards that vest upon the passage of time, expense is being recorded over the vesting period. Performance-based awards are expensed over the requisite service period based on probability of achievement.

The estimated fair value of the Company's stock-based awards, less expected annual forfeitures, is amortized over the awards' service period. The total unrecognized compensation cost for unvested outstanding stock options was less than $

0.1

million at

December 31, 2020

. This expense will be recognized over a weighted average expense period of approximately

0.4

years. The total unrecognized compensation cost for unvested outstanding restricted stock was $

5.2

million at

December 31, 2020

. This expense will be recognized over a weighted-average expense period of approximately

1.9

years.

The Company did

not

grant any stock options during the

nine

months ended

December 31, 2020

. The Company granted

5,939

stock options during the

nine

months ended

December 31, 2019

. The stock options granted during the

nine

months ended

December 31, 2019

will vest over

ars. The weighted average assumptions used in the Black Scholes valuation model for stock options granted during the

nine

months ended

December 31, 2019

are as follows:

Three Months Ended December 31,

Nine Months Ended December 31,

2020

2019

2020

2019

Expected volatility

N/A

66.5

Risk-free interest rate

N/A

1.8

Expected life (years)

N/A

5.91

Dividend yield

N/A

None