FMVSS 121 applies to trucks, buses and trailers equipped with air brake systems and establishes performance and equipment requirements. The Technology & Maintenance Council Recommended Practice #628B (T.M.C. RP 628B) provides information for judging the performance of aftermarket brake linings on air-actuated foundation brakes.

SAE J2975 testing and its report with the environmental letter coding per SAE J866 are valuable tools to: determine the level of compliance to state rules and regulations for heavy metals and asbestiform fiber content, compare different friction material formulations, and support the declaration of conformity requirements for vehicle manufacturers, distributors, wholesalers, retailers, installers, and friction material suppliers.