This Standard covers pressure-temperature ratings, materials, dimensions, tolerances, marking, and testing for pipe flanges in sizes NPS 26 through NPS 60. Included are flanges with rating class designations 75, 150, 300, 400, 600, and 900 with requirements given in both SI (Metric) and U.S. Customary units, with diameter of bolts and flange bolt holes expressed in inch units. This Standard is limited to (a) flanges made from cast or forged materials, (b) blind flanges made from cast, forged, or plate materials (see Tables 1 and 2). Also included in this Standard are requirements and recommendations regarding flange bolting, flange gaskets, and flange joints.