NEMA ANSI C 80.6:2018

This standard covers the requirements for steel electrical intermediate metal conduit for use as a raceway for wires or cables of an electrical system. Finished conduit is produced in nominal 10 ft. (3.05 m) lengths, threaded on each end with one coupling attached. It is protected on the exterior surface with a metallic zinc coating or an alternate corrosion protection coating (See UL 1242 for alternate corrosion-resistant coating(s) requirements) and on the interior surface with a zinc or organic coating.
This standard also covers conduit couplings, elbows, and conduit lengths other than 10 ft. (3.05 m). Properly assembled systems of conduit, couplings, elbows, and nipples manufactured in accordance with this standard, and other identified fittings, provide for the electrical continuity required of an equipment grounding conductor.