This part of IEC 61249 gives requirements for properties of cyanate ester, brominated epoxide modified or unmodified woven E-glass laminate sheets of defined flammability (vertical burning test), copper-clad, in thicknesses of 0,05 mm to 3,2 mm. The flammability rating is achieved through the use of brominated fire retardants contained as an integral part of the epoxide polymeric structure. The glass transition temperature is defined to be 160 °C minimum. Some property requirements may have several classes of performance. The class desired needs to be specified on the purchase order otherwise the default class of material may be supplied.