FKM — Fluoroelastomer

FKM, acronym for fluoroelastomer, is a family of synthetic rubbers with high chemical, thermal, and aging resistance. It's the same material used by leading submersible watch manufacturers for high-end rubber straps. It resists temperatures from -20°C to +200°C, saltwater, oils, solvents, and UV rays without degrading. It's the top of the line for sport and diving straps, more expensive than common silicone or natural rubber but with significantly greater durability.