ISO 3601-4:2008

ISO 3601-4:2008 specifies dimensions and tolerances for five types of anti-extrusion rings, which are also known as back-up rings: spiral type (T1); angle cut type (T2); solid type (T3); angle cut concave type (T4); solid concave type (T5). These anti-extrusion rings are for use with selected O-ring sizes as specified in ISO 3601-1 and the relevant housing dimensions specified in ISO 3601-2.