This part of IEC 62317 specifies the dimensions that are of importance for mechanical interchangeability for E-cores with rectangular cross-section made of ferrite, the dimensions of coil formers to be used with them, and the effective parameter values to be used in calculations involving them. The selecting core sizes to this standard is based on the philosophy of including those sizes, which are industrial standards, either by inclusion in national standards, or by broad-based use in industry. See IEC 62317-1 for more detail concerning the philosophy of selecting core sizes to be included. NOTE Cores covered by this standard are intended for general applications at both low and high flux densities, but they also find uses in special applications such as pulse transformers. They are generally used in pairs. Whilst the main application of this standard is expected to be for ferrite cores, its validity for iron powder cores should not be overlooked. Coil formers are not specified for E-cores smaller than E 8/2, which are also used in SMD assemblies. The use of “derived” standards, which give a more detailed specification of component parts whilst still permitting compliance with this standard, is discussed in Annex A.