6. Inventories

Inventories consisted of the following (in millions):

	March 31,		December 31,
	2013		2012
Raw materials	$	203.6	$	199.0
Work-in-process	197.8		197.0
Finished goods	166.6		160.5
Demonstration units	53.7		55.0
Inventories	$	621.7	$	611.5

Finished goods include in-transit systems that have been shipped to the Company’s customers, but not yet installed and accepted by the customer. As of March 31, 2013 and December 31, 2012, inventory-in-transit was $82.8 million and $93.9 million, respectively.

The Company reduces the carrying value of its demonstration inventories for differences between its cost and estimated net realizable value through a charge to cost of product revenue that is based on a number of factors, including the age of the unit, the physical condition of the unit and an assessment of technological obsolescence. Amounts recorded in cost of revenue related to the write-down of demonstration units to net realizable value were $7.8 million and $6.8 million for the three months ended March 31, 2013 and 2012, respectively.