IEC 61249-2-31:2009 specifies requirements for properties of modified epoxide woven E-glass laminate sheet of a thickness of 0,05 mm up to 3,2 mm, of defined flammability (vertical burning test), copper-clad. The glass transition temperature is defined to be 150 °C minimum. The relative permittivity is equal to or less than 4,1 and the dissipation factor is equal to or less than 0,0120 at 1 GHz.