Industry rules and guidelines support/mandate equivalency, but provide very little guidance on how to realize MPP substitution. Currently, industry guidelines fail to provide adequate direction to maintenance facilities for material, process, and part equivalencies. Suitable substantiation procedures to be able to select alternate materials are demanded by the air transport industry. The purpose of ARINC Report 670 is to provide clear definitions for materials, processes, parts, substantiation requirements, decision boundaries and limitations, and a standard process for equivalency determination. This report is intended as general guidance for avionics maintenance facilities; however, this does not preclude its use for other sectors of aircraft maintenance as appropriate.