This part of IEC 60317 specifies general requirements of glass-fibre wound resin or varnish impregnated, bare or enamelled, round copper winding wires. The range of nominal conductor diameters is given in the relevant specification sheet. When a reference is made to a winding wire according to one of the IEC 60317 series, the following information should be given in the description: – reference to IEC specification; – nominal conductor diameter in millimetres; – grade of coating and glass covering. The coating shall be characterised by the following different grades of thickness: – GL1, bare conductor with 1 layer of glass fibre – GL2, bare conductor with 2 layers of glass fibre – grade 1 GL1, enamelled grade 1 (grade 1) with 1 layer of glass fibre (GL1) – grade 1 GL2, enamelled grade 1 (grade 1) with 2 layers of glass fibre (GL2) – grade 2 GL1, enamelled grade 2 (grade 2) with 1 layer of glass fibre (GL1) – grade 2 GL2, enamelled grade 2 (grade 2) with 2 layers of glass fibre (GL2)