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, 2014			December 31, 2013
	(in thousands)
Raw materials	$	33,694		$	28,592
Work in process	2,249			2,286
Finished goods	2,099			1,841
	38,042			32,719
Less: Allowance for excess and obsolete inventories	(802		)	(579		)
Total, net	$	37,240		$	32,140

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



	Three months ended				Nine months ended
	September 30, 2014		September 30, 2013		September 30, 2014		September 30, 2013
Allowance for excess and obsolete inventories:	(in thousands)
Balance, beginning of period	$	735	$	537	$	579	$	363
Provisions for excess and obsolete inventories	67		267		223		468
Inventories written off	—		—		—		(27		)
Balance, end of period	$	802	$	804	$	802	$	804