The purpose of this report is to give recommendations of the co-ordination of dimensions between enclosures and built-in devices for rail fixing for household or similar installations by listing the principal overall and related mounting dimensions, the rated current of a single device not exceeding 125 A. Examples of these devices are: MCBs, RCDs switches, fuse-systems, indicating lamps, relays, socket-outlets, timing switches, etc. Compliance with this document does not preclude the need for compliance with other relevant specifications. This document needs not apply to type tested and partially type tested assemblies which are covered by other specifications. The means of fixing envisaged in this document are mounting rails. Other possible means of fixing may be used but are not covered by these recommendations. NOTEThe only criterion chosen in this document for co-ordination of dimensions has been the geometry of the devices. When selecting the enclosure, other criteria should be taken into account, e.g. the rated current of the devices.