The requirements cover aluminum and stainless steel electrical rigid metal conduit (RMC), nipples, elbows, and couplings in trade sizes 3/8 &8211; 6 (12 &8211; 155), for use as a metal raceway for the installation of wires and cables in accordance with the National Electrical Code. Steel conduit provided with an exterior coating of zinc or a zinc-based, nonmetallic, or other alternate corrosion-resistant material and an interior coating of an organic or zinc material, is covered by the Standard for Electrical Rigid Metal Conduit &8211; Steel, UL 6.