Describes up to DN 4000, PN 2.5 to 40 grey ductile and malleable cast iron circular flanges. Specifies the types of cast iron flanges and their facings, tolerances, dimensions, threading for malleable cast iron flanges, flange face surface finish, bolt sizes, marking and materials for flange and bolting materials together with associated pressure/temperature ratings. Also gives detailed definitions for nominal size (DN) and nominal pressure (PN). Includes several appendices and tables.