Historical
NEMA RN 1:2005
Polyvinyl-chloride (pvc) externally coated galvanized rigid steel conduit and intermediate metal conduit
Covers continuous PVC exterior coatings and corrosion-resistant interior coatings, as well as galvanized steel conduit, galvanized steel IMC, threaded couplings and elbows to which they may be applied.
NEMA: National Electrical Manufacturers Association [nema]