INVENTORY - Schedule of Inventory (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Inventory Disclosure [Abstract]
Raw materials	$ 6,798,000		$ 6,798,000		$ 4,064,000
Work-in-process	356,000		356,000		531,000
Finished goods	461,000		461,000		342,000
Total inventories	7,615,000		7,615,000		$ 4,937,000
Write-down in cost of sales	$ 800,000	$ 0	$ 1,200,000	$ 0