Fluroelastomer or FKM is a class of synthetic rubber designed for very high temperature operation. FKM provides extraordinary levels of resistance to chemicals, heat and oil, while providing useful service life above 200°C. FKM are not a single entity but a family of fluoropolymer rubbers. Fluoroelastomers or FKM (sometimes also referred to as FKM Viton) can be classified by their fluorine content, 66%, 68%, 70% respectively. It means that FKM rubber having higher fluorine content, have increasing fluids resistance derived from increasing fluorine levels.