Revenue Recognition Revenue from all customers, including distributors, is recognized when all significant contractual obligations have been satisfied, pricing is fixed and determinable and collection of the resulting receivable is reasonably assured. Generally, product revenues are recognized upon shipment under Ex-works terms, and include shipping and handling costs. Revenue from services is recognized as work is performed. Taxes collected from customers and remitted to governmental authorities are excluded from revenue on the net basis of accounting. Estimated returns and warranty costs are recorded at the time of sale. Sales of some inspection system products may require customer acceptance due to performance or other acceptance criteria included in the terms of sale. For these inspection system product sales, revenue is recognized at the time of customer acceptance. Our multiple deliverable arrangements typically include the sale of an inspection system or metrology product, related installation and training and, in some cases, an extended warranty. Revenue from installation and training are recognized as the services are provided. Revenue from extended warranties is recognized ratably over the warranty period. When a sale involves multiple elements, revenue is allocated to each respective element at inception of an arrangement using the relative selling price method. Selling price is determined based on a selling price hierarchy, consisting of vendor specific objective evidence (VSOE), third party evidence or estimated selling price. Managements best estimate of the selling price of an inspection system and metrology products is based on the cost of the product and a reasonable margin based on geographic location and competitive market conditions. We use VSOE to establish fair value for extended warranty, installation and training services. If VSOE is not available to establish fair value for extended warranty, installation and training services, we estimate a selling price based on the cost-build-up for t