Concentric PTFE Lining Valve also known as fluorine plastic lined corrosion resistant valves, are fluorine plastic molded into the inner wall of the steel or iron valve bearing parts or the outer surface of the valve inner parts. Fluorine plastics here mainly include: PTFE, PFA, FEP and others. FEP lined butterfly, teflon coated butterfly valve and FEP lined butterfly valve are usually used in strong corrosive media.