Applies to couplings for non-passenger-carrying caravans and trailers, and specifies standard dimensions, with tolerances where necessary, for integral type and casting-with-bolt type 50-mm coupling ball, together with three ratings of attaching coupling bodies. Material requirements, design, features affecting function and safety, marking, finish, and strength tests for longitudinal and vertical loading in tension and compression and for transverse thrust are given, and an appendix sets out conditions of attachment of the ball coupling.