Isovolta 4373 is a class F 155 °C tape composed of a woven glass fabric, mica paper and with a polyester mat covering the mica paper. It is designed for use in vacuum pressure impregnation (VPI) applications. The binder is a modified epoxy resin, uncatalyzed and fully compatible with most commonly used VPI resins. - Because of the low resin content, the tapes and wrappers are very porous, very flexible and conformable allowing tight hand or machine winding around both straight and irregular surfaces thereby helping to reduce air voids and therefore, the possibility of internal corona discharges.