Details on the FKM material: For those who don’t know, FKM stands for Fluoroelastomer, which is a class of man-made rubber of great density but soft in touch, made to stand harsh conditions, such as high temperature, chemicals etc. For example, this type of rubber is often used in aerospace and nautical industries, which speaks a lot about its quality. To name a few, some of the characteristics of this material are: excellent resistance to chemicals (oxidation, acids, fuels), astonishing temperature durability (from - 60°C to 225°C ), great stability in all weather conditions, long lasting etc. The material wass first developed by American company DuPont, under the brand name Viton®. The same company developed Neoprene™, which became so popular that it became common name for polychloroprene. The same often happens with Viton. Nowadays, there are many other producers of this valuable material. There are also variations of FKM, based on the polymers used.