Inventories

3 Months Ended

Mar. 31, 2019

Inventories [Abstract]

Inventories

4. Inventories

Inventories as of December 31, 2018 and March 31, 2019 consisted of the following:

	December 31,		March 31,
	2018		2019
Raw materials	$	1,675,383	$	1,455,516
Work in progress		2,737,415		1,373,975
Finished goods		5,209,563		6,386,132
	$	9,622,361	$	9,215,623

During the three months ended March 31, 2018 and 2019, write-downs of obsolete inventories to lower of cost or market of $1,199 and $62,772, respectively, were charged to cost of revenues.