This document specifies the dimensions of non-knife-edge flanges and collars used in vacuum technology. The dimensions ensure interchangeability between bolted, clamped and rotatable flanges: a) whether the assembly be homogeneous (for example, bolted flanges or clamped flanges) or heterogeneous (for example, bolted flanges assembled with clamped flanges either by means of bolts or clamps or by means of bolts and rotatable flanges). b) whether the sealing rings used with the flanges be elastomer O-rings or metal sealing rings, provided that they are compatible with the linear sealing loads given in Annex A.