Defines essential dimensions, to ensure interchangeability of bushings and to ensure adequate mounting and interchangeability of mating plug-in separable connectors of equivalent ratings. Pertains to ceramic and resin insulated bushings for rated voltages above 1 kV up to 36 kV rated currents from 250 A up to 3150 A and frequencies from 15 Hz up to 60 Hz for insulating liquid filled transformers.