stock-based compensation	3 Months Ended
Mar. 31, 2021
Share-based Payment Arrangement [Abstract]
stock-based compensation	5. stock-based compensation The Company accounts for stock-based compensation based on the fair value of the stock or stock-based instrument on the date of grant. The Company recognized a net total of $343,727 and $347,185 of stock-based compensation expense for the three months ended March 31, 2021 and 2020, respectively. During the three months ended March 31, 2021, the Company granted 135,512 restricted stock units (“RSUs”) to its board of directors as partial compensation for the 2021 year. In January 2020, the Company granted 73,350 RSUs to its board of directors as partial compensation for the 2020 year. RSUs vest quarterly on a straight-line basis over a one-year period. For the three months ended March 31, 2021 and 2020, approximately $284,000 and $258,000, respectively, of non-cash compensation expense related to the RSU grants to the board of directors are included selling, general and administrative expenses. During the three months ended March 31, 2021, the Company did not grant any shares of common stock to employees. For the three months ended March 31, 2021 and 2020, approximately $48,000 and $72,000, respectively, of compensation expense are included in selling, general and administrative expenses and approximately $11,000 and $18,000, respectively, of compensation expense are included in cost of sales for shares of common stock granted to employees between 2016 and 2020.

stock-based compensation

3 Months Ended

Mar. 31, 2021

Share-based Payment Arrangement [Abstract]

5. stock-based compensation

The Company accounts for stock-based compensation based on the fair value of the stock or stock-based instrument on the date of grant. The Company recognized a net total of $343,727 and $347,185 of stock-based compensation expense for the three months ended March 31, 2021 and 2020, respectively.

During the three months ended March 31, 2021, the Company granted 135,512 restricted stock units (“RSUs”) to its board of directors as partial compensation for the 2021 year. In January 2020, the Company granted 73,350 RSUs to its board of directors as partial compensation for the 2020 year. RSUs vest quarterly on a straight-line basis over a one-year period. For the three months ended March 31, 2021 and 2020, approximately $284,000 and $258,000, respectively, of non-cash compensation expense related to the RSU grants to the board of directors are included selling, general and administrative expenses.

During the three months ended March 31, 2021, the Company did not grant any shares of common stock to employees. For the three months ended March 31, 2021 and 2020, approximately $48,000 and $72,000, respectively, of compensation expense are included in selling, general and administrative expenses and approximately $11,000 and $18,000, respectively, of compensation expense are included in cost of sales for shares of common stock granted to employees between 2016 and 2020.