IEC 60471:2020 applies to string insulator units of the cap and pin type and also of the long rod type as well as the fittings used with such insulators. The object of this document is to define the dimensions of a series of clevis and tongue couplings to permit the assembly of insulators or fittings supplied by different manufacturers. This third edition cancels and replaces the second edition published in 1977. This edition includes the following significant technical changes with respect to the previous edition: - there are no new clevis and tongue couplings; - For the dimensions of the existing designated size of couplings that characterize the same location, the effective number of the size is unified.