Annual report pursuant to Section 13 and 15(d)

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Warranty Reserve (Details)

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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Warranty Reserve (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES    
Standard assurance warranty period 1 year  
Movement in Standard Product Warranty Accrual [Roll Forward]    
Warranty reserve, at the beginning of the year $ 1,491 $ 116
Additions to warranty reserve 346 2,352
Claims fulfilled (284) (977)
Warranty reserve, at the end of the period $ 1,553 $ 1,491