Is made of asbestos rubber sheet or non asbestos gaskets and Teflon coated sheet combination, type V (cutting type) PTFE envelope gasket by PTFE mechanical turning, type U (folded package type) PTFE envelope gasket by PTFE with edge heating has excellent bonding. The corrosion resistance and good compression resilience, widely used in all kinds of strong acid, strong alkali, chlorine oxidation, sealing and not allow pollution. Medium is usually in low pressure position,.