Perflourelastomers (FFKM) is a terpolymer of tetrafloureten (TFE) and perflourmetylvinyleter (PMVE).

The material has a better resistance to thermal, oxidative and chemical degradation than flourelastomer. The material is extremely expensive.
About 50 times than Flourelastomer (FPM). used in the oil extraction industry and in chemical analysis instruments.