GREAT PTFE encapsulated O-rings fall within the category of FEP/PFA encapsulated silicone/viton O-rings which are made of special heat resistant rubber coated by fluoride plastic with unique manufacture technique. Therefore,they possess the characteristic of low permanent deformation rate given by rubber O-ring,along with the special features endowed by fluoride plastic such as resisting heat,cold,oil,rub,climate changers and chemical corrosion.