SUNPASS FEP-/PFA-encapsulated O-rings are constructed with a resilient elastomer core, surrounded by a flawlessly bonded shell of modified PTFE. The core, fashioned from FKM (Viton), ensures consistent pretensioning at the seal interface. The unbroken casing is made from FEP (fluorinated ethylene propylene) or PFA (perfluoroalkoxy copolymer), providing dependable sealing and robust protection against corrosive substances. This design yields efficacy akin to that of pure PTFE materials.