ISO TS 20825:2003 specifies the maximum allowable wear and the limit dimensions of worn components of in-use mechanical couplings, which, when respected, will ensure the safe operation on the road of the heavy commercial vehicles fitted with such couplings. It is applicable to 40 mm and 50 mm drawbar couplings, 40 mm and 50 mm drawbar eyes, 50 mm and 90 mm fifth wheel kingpins, and hook couplings and toroidal eyes.