MSS - Manufacturers Standardization Society of the Valve and Fittings Industry.
Scope
This MSS Standard Practice applies to the spot facing for U.S. customary (inch series) bolting of pipe flanges in bronze@ gray iron@ ductile iron or steel when cast integral with valves and fittings@ as well as the companion flanges@ when so required by the standard for the product. This Standard Practice also applies to the spot facing for metric bolting used in bolted joints not covered by the reference flange standards herein.