Inventories

3 Months Ended

Mar. 31, 2020

Inventories [Abstract]

Inventories

4. Inventories

Inventories as of December 31, 2019 and March 31, 2020 consisted of the following:

	December 31,		March 31,
	2019		2020
Raw materials	$	482,836	$	598,039
Work in progress		1,254,490		1,718,101
Finished goods		6,929,388		5,113,489
	$	8,666,714	$	7,429,629

During the three months ended March 31, 2019 and 2020, write-downs of obsolete inventories to lower of cost or market of $62,772 and $409,062, respectively, were charged to cost of revenues.