Black Fluorocarbon/ Fluoroelastomer O ring, also known as a Viton o-ring or FKM, FPM orings.
FKM (Viton ®) O'Rings have a low compression set and have high temperature and chemical resistance. The terms FPM, FKM and Viton® very often cause confusion and lead to incorrect interpretations.
All of these designations actually stand for one single base material: fluoro rubber. Temperature Range -20°C to +200°C with Durometer / Hardness 75.
Buna-N is a copolymer of Acrylonitrile and Butadiene. Nitrile is the most commonly used elastomeric material for molded and extruded products. This material offers relative low cost, good mechanical properties, and resistance to many common oils, fuels and lubricants. NBR has poor resistance to weathering, sunlight and ozone so it is best used in enclosed environments where parts are not exposed to the elements.
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