Revenue

The Company differentiates revenue and cost of revenue based on whether the source of revenue is attributable to products, rentals or services. Revenue and cost of revenue by source are as follows (in thousands):



	Year ended December 31,
	2015		2014		2013
Revenue:
Products	$	283,493	$	354,356	$	282,639
Rentals	35,242		65,549		62,042
Services	15,624		29,252		26,384
	$	334,359	$	449,157	$	371,065
Cost of Revenue:
Products	$	187,511	$	214,417	$	180,800
Rentals	16,052		31,285		24,987
Services	8,668		12,385		9,916
Depreciation	7,018		8,111		7,835
	$	219,249	$	266,198	$	223,538