Couplings from AFT Fasteners are composed of durable black iron or galvanized malleable iron and are 100% pressure tested right at the factory. They are UL, FM listed and made in compliance to ASME standards. AFT's couplings are made in an array of sizes for residential gas, air, and lp applications. The galvanizing is done by a hot dip process which is in accordance to ASTM A153. AFT's couplings are available in sizes for all residential water applications. They are not for use with drinking water. Always check your local plumbing and gas codes before starting any piping projects.