This part of ISO 11900 specifies the dimensions and tolerances, in millimetres, of reduced ball-lock punch retainers, type E, for heavy duty, and of their backing plug, the main use being retention of ball-lock punches in accordance with ISO 10071-2, when punching holes in steel sheets. It also gives material guidelines and hardness requirements, and specifies the designation of ball-lock punch retainers in accordance with this part of ISO 11900.