IEC 60317-58:2010 specifies the requirements of enamelled rectangular copper winding wire of class 220 with a sole coating based on polyamide-imide resin, which may be modified providing it retains the chemical identity of the original resin and meets all specified wire requirements. Class 220 is a thermal class that requires a minimum temperature index of 220 and a heat shock temperature of at least 240 °C.