SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Inventories (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Inventories
FIFO inventory amount	$ 1,183,000	$ 1,127,000
Reserve for inventory obsolescence	7,000	5,000
Major components of inventories
Raw materials	1,428,924	1,438,471
Work-in-progress	423,186	355,208
Finished goods	1,416,547	1,319,856
Reduction to LIFO cost	(1,182,592)	(1,127,363)
Total inventories	$ 2,086,065	$ 1,986,172