FEP Encapsulated O Ring also known as PTFE Encapsulated 'O' Ring consist of a seamless PTFE jacket which surrounds the elastomer core providing the chemical inertness, and thus ensures sealing function and high resistance to corrosive media. Whilst the elastomer core energises the seal and provides even tension at the sealing point and thus a constant area pressure. Encapsulated seals were primarily designed to solve the growing problems of sealing corrosive fluids in industry, Development of FEP encapsulated seals provided designers and engineers with a seal that combined the chemical resistance of PTFE with the resilience of rubber. Encapsulated seals are available with two types of PTFE jacket, FEP which is standard, and PFA for more demanding applications. The energising core is available in FKM or Silicone