This section of IEC 917-2 is a detail specification which is to be used in whole or in part in all fields of electronics where devices and systems are designed according to the sectional specification IEC 917-2. The dimensions in the tables of this detail specification are a selection from the sectional specification IEC 917-2. All other sizes from the sectional specification are valid in this detail specification provided the relationship between the dimensions is maintained, i.e. the dimensional difference between the co-ordination dimensions HC ,Wc and Dc and dimensions Hc0, Hc1 , Hc2 ; Wc0 , Wc1 and Dco, Dc1 shown in tables 1, 2 and 3 are to be maintained. The purpose of this publication is the specification of dimensions which will ensure mechanical interchangeability of cabinets and racks, and ensure mechanical interchangeability for subrack mounting. Cabinets and racks can be arranged together to form larger operating units. Application of specific cabinets or racks, attachments and accessories, such as heat exchangers, control elements, switches, etc. does not form part of this specification.