ISO 5821:2009 specifies the dimensions and tolerances of resistance spot welding electrode caps, where a female taper is used to fix the cap to an electrode adaptor.

ISO 5821:2009 applies only to electrode caps for which the electrode force given for diameters 13 mm, 16mm and 20 mm (taper 1:10) and for diameters 12,7 mm, 15,8 mm and 19,1 mm (taper 1:9,6) is not exceeded.