Applies to string insulator units of the can and pin type and also of the long rod type as well as to the fittings used with such insulators. Defines dimensions of a series of clevis and tongue couplings to permit the assembly of insulators or fittings supplied by different manufacturers. Note: - For co-ordination between standardized dimensions and strength classes of cap and pin type insulators and long rod type insulators see IEC 305 and 433.