This part of ISO 11900 specifies the dimensions and tolerances, in millimetres, of reduced ball-lock punch retainers, type C and type D, for light duty, and of their backing plug, the main use of which is the retention of ball-lock punches in accordance with ISO 10071-1, when punching holes in steel sheets. It also gives material guidelines and specifies the hardness and designation of ball-lock punch retainers that are in accordance with its specifications.