There are two main types of specification: performance specification and conformance specification (sometimes called prescriptive or technical specifications).

A conformance specification establishes the characteristics a commodity must possess, including details of how the commodity will be manufactured; engineering plans, drawings, or blueprints may be included. The design specification states in prescriptive terms what the potential offeror must provide to the buyer.

Conformance specifications have following features:

- Focus on inputs

- Give specific method, processes and materials

- May identify specific manufacturers or components

- The 'how' as well as the 'what'

- Ties supplier to set details