Revenue Recognition The Company recognizes revenue when all of the following criteria are met: persuasive evidence of an arrangement exists, delivery has occurred, the sales price is fixed or determinable, and collectibility is reasonably assured. Revenue from the sale of the Companys disposable products is recognized when products are shipped to the customer and title transfers. In general, customers do not have a right of return for credit or refund. However, the Company allows returns under certain circumstances and records an allowance for sales returns based upon an analysis of revenue transactions and historical experience of sales returns. Write-offs to customer account balances for product returns are charged against the allowance for sales returns. Revenue from the sale of CVX-300 laser systems is recognized after completion of contractual obligations, which generally include delivery and installation of the systems. The Companys field service engineers are responsible for installation of each laser system. The Company generally provides a one-year warranty on laser sales, which includes parts, labor and replacement gas. Upon expiration of the warranty period, the Company offers similar service to its customers under annual service contracts or on a fee-for-service basis. Revenue from fee-for-service arrangements is recognized upon completion of the related service. The Company accounts for service provided during the one-year warranty or service contract period as a separate unit of accounting. As such, the fair value of this service is deferred and recognized as revenue on a straight-line basis over the related warranty or service contract term, and warranty and service costs are expensed in the period they are incurred. Revenue recognized associated with service performed during the warranty period totaled $0.6 million , $0.7 million and $0.7 million for the years ended December 31, 2015 , 2014 and 2013 , respectively. The Company offers four laser system placement programs, which are described belo