... Epoxy Sheet (FR4 insualtion parts)is insulation class B(130 degree),with good dielectric stability at high humidity, ROSH Fr-4 Epoxy Glass Cloth Laminated Sheet ... (FR4 sheet,FR4 insualtion parts)is made of electrical non ... ,transformers,ect.Fr4 is flame retardant. FR4 Epoxy Glass Cloth Laminated Sheet,With ROSH Certification