Annual report pursuant to Section 13 and 15(d)

Accrued Expenses - Changes in Accrued Warranty Obligations (Details)

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Accrued Expenses - Changes in Accrued Warranty Obligations (Details) - USD ($)
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Accrued Expenses      
Accrued Warranty Obligation $ 218,047 $ 167,503 $ 41,132
Reductions for Settling Warranties (204,583) (257,173) (157,035)
Warranties Issued During Period 85,429 307,717 283,406
Accrued Warranty Obligations $ 98,893 $ 218,047 $ 167,503