The federal government has exact specifications for most of the products and services it buys on a regular basis. In all likelihood, your contract will contain such precise specifications. In fact, the specifications -- which describe the government's requirements -- were contained in the invitation for bids or request for proposals on which you based your bid or proposal.
Once an award is made to your company, you are contractually bound to deliver the product or service described in the specifications. Sometimes, the basic specifications will make reference to and incorporate other federal specifications. You are, of course, bound by the terms of these specifications as well as the basic specifications. Failure to deliver a product meeting these terms may result in termination of your contract by default.
Accordingly, as mentioned previously, never bid on a contract unless you have read and understood all of the specifications. Also, read the specifications again before you start work under the contract.
Information courtesy of the Small Business Administration.