4. Inventories

Inventories as of December 31, 2017 and 2016 consist of the following (in thousands):


	Year Ended December 31,
	2017			2016
Finished goods		13,737			7,867
Semi-finished goods and work-in-process		53,148			46,653
Raw materials		12,445			7,846
Materials in-transit		134			1,859
Less: inventory reserve		(6,391	)		(7,177	)

Inventories, net	$	73,073		$	57,048

Changes in inventory reserve for the years ended December 31, 2017, 2016 and 2015 are as follows (in thousands):


	Year Ended December 31,
	2017			2016			2015
Beginning balance	$	(7,177	)	$	(16,033	)	$	(47,488	)
Change in reserve
Inventory reserve charged to costs of sales		(4,789	)		(7,646	)		(13,635	)
Sale of previously reserved inventory		3,784			4,985			13,932

		(1,005	)		(2,661	)		297
Write off		2,620			11,384			29,146
Translation adjustments		(829	)		133			2,012

Ending balance	$	(6,391	)	$	(7,177	)	$	(16,033	)

Inventory reserve represents the Company’s best estimate in value lost due to excessive inventory level, physical deterioration, obsolescence, changes in price levels, or other causes based on individual facts and circumstances. Inventory reserve relates to inventory items including finished goods, semi-finished goods and work-in-process. Write off of this reserve is recognized only when the related inventory has been disposed or scrapped.