Inventories consist of raw materials and components, such as drivers, metal sheet and coil stock and molded parts; work in process inventories, such as frames and reflectors; and finished goods, including completed fixtures and systems, and accessories. All inventories are stated at the lower of cost or net realizable value with cost determined using the first-in, first-out (FIFO) method. Orion reduces the carrying value of its inventories for differences between the cost and estimated net realizable value, taking into consideration usage in the preceding 9 to 12 months, expected demand, and other information indicating obsolescence. Orion records, as a charge to cost of product revenue, the amount required to reduce the carrying value of inventory to net realizable value. As of March 31, 2019 and 2018, Orion's inventory balances were as follows (dollars in thousands):

	Cost		Excess and Obsolescence Reserve			Net
As of March 31, 2019
Raw materials and components	$	9,161	$	(1,393	)	$	7,768
Work in process		1,010		(269	)		741
Finished goods		6,056		(1,162	)		4,894
Total	$	16,227	$	(2,824	)	$	13,403
As of March 31, 2018
Raw materials and components	$	6,073	$	(1,363	)	$	4,710
Work in process		1,190		(263	)		927
Finished goods		3,934		(1,745	)		2,189
Total	$	11,197	$	(3,371	)	$	7,826

Costs associated with the procurement and warehousing of inventories, such as inbound freight charges and purchasing and receiving costs, are also included in cost of product revenue.