This part of IEC 61249 gives requirements for properties of cyanate ester, brominated epoxide modified or unmodified, reinforced woven E-glass laminate sheet of defined flammability (vertical burning test), copper-clad in thicknesses of 0,05 mm to 3,2 mm. The flammability rating is acheived 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.