This part of IS0 7005 for a single system of flanges specifies requirements for circular grey, malleable and ductile cast iron flanges in the following nominal pressure ratings: Series 1 * Series 2 * IS0 PNlO IS0 PN2,5 IS0 PN16 IS0 PN6 IS0 PN20 IS0 PN25 IS0 PN50 IS0 PN40 This part of IS0 7005 specifies the types of flanges and their facings, dimensions, bolt sizes, surface finish of faces, marking, testing, inspection and materials together with associated pressure/temperature ratings. NOTES 1 Attention is drawn to the need to refer to the pressure/temperature rating tables for the permissible working pressures, particularly for flanges of IS0 PN20 and IS0 PN50. 2 Dimensions of gaskets will be the subject of a future International Standard.