This standard establishes the characteristics that connection assemblies (enclosure and connection element) for underground low-voltage electrical distribution networks shall comply and the tests that shall be passed. This standard is applicable to connection assemblies (enclosure and connection element) for splices, derivations and terminations of single-pole cables with aluminium conductors, according to the UNE-HD 603 Standards, parts 5N and 5X. The designation of the preferred constructions of the accessories of this standard indicates the range of maximum and minimum admissible sections of each model. It does not imply that the accessory is designed to be used in all intermediate sections. This standard is not extended to the connection elements supplied independently included in the UNE 211024 Standard, nor to the isolated connections included in the UNE 211022 Standard.