O-rings coated with FEP have an elastic core made of Viton® (FKM), silicone (VMQ) or EPDM. The respective core is seamlessly encapsulated with FEP. The strength of the FEP coating depends on the cord size of the O-ring.
The chemical properties of FEP correspond largely to those of pure PTFE. That's why FEP-coated O-rings are resistant to most chemicals and solvents.
FEP is a FDA approved material for food contact parts.