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Reference.org
Form, fit and function
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<p>Form, Fit, and Function (also F3 or FFF) is a concept used in various industries, including manufacturing, engineering, and architecture, to describe aspects of a product's design, performance, and compliance to a specification. F3 originated in <a href="/facts/Military_logistics/rm7npHRQ">military logistics</a> to describe interchangeable parts: if F3 for two components have the same set of characteristics, i.e. they have the same shape or <i>form</i>, same connections or <i>fit</i>, and perform the same <i>function</i>, they can be substituted one for another. The idea behind F3 is to contractually require the original manufacturer to provide the customer (US government) with the free use of F3 data so that the customer can <a href="/facts/Second_source/Ma2HVMbm">second source</a> the part and thus enable <a href="/facts/Competition/FpQaEhHv">competition</a> between multiple suppliers. In practice, F3 is usually used not for final products (like entire <a href="/facts/Weapon_systems/IoMkCbpk">weapon systems</a>), but for the procurement of components and subsystems. </p><p>FFF refers to a set of characteristics or requirements that are essential for the design and compatibility of products, components, or systems, and can have legal considerations in regulated industries like aviation and defense (e.g., for technical data rights and configuration management). </p><p>The concept originates in the 1960s, and in some cases called "form-fit-function". The United States (US) Government formally recognized it in the legal incorporation of Public Law 98-525 regarding technical data and design changes. F3 can also refer to the ability of a replacement unit or technology upgrade to be compatible with existing systems, or be compatible with change control procedures (e.g., NASA's use in reliability via military standards). </p>