Inventories

Inventories are valued at the lower of cost or market. Cost is determined by the first-in, first-out (“FIFO”) method. We establish an allowance for excess and obsolete inventories based on product line changes, the feasibility of substituting parts and the need for supply and replacement parts.



	September 30, 2013			December 31, 2012
	(in thousands)
Raw materials	$	27,096		$	28,155
Work in process	3,691			2,757
Finished goods	3,400			2,065
	34,187			32,977
Less: Allowance for excess and obsolete inventories	(804		)	(363		)
Total, net	$	33,383		$	32,614

The related changes in the allowance for excess and obsolete inventories account are as follows:



	Three months ended				Nine months ended
	September 30, 2013		September 30, 2012		September 30, 2013			September 30, 2012
Allowance for excess and obsolete inventories:	(in thousands)
Balance, beginning of period	$	537	$	300	$	363		$	300
Provisions for excess and obsolete inventories	267		—		468			—
Inventories written off	—		—		(27		)	—
Balance, end of period	$	804	$	300	$	804		$	300