This Standard pertains primarily to cast Class 125 and Class 250 bronze threaded pipe fittings. Certain requirements also pertain to wrought or cast plugs, bushings, couplings, and caps. This Standard covers: (a) pressure-temperature ratings; (b) size and method of designating openings of reducing pipe fittings; (c) marking; (d) minimum requirements for casting quality and materials; (e) dimensions and tolerances in U.S. customary and metric (SI) units; (f) threading.