Polytetrafluoroethylene (PTFE) is chemically inert to almost everything, has the lowest coefficient of friction of any solid polymer, and operates from cryogenic temperatures to roughly 500°F (260°C). It is not an elastomer: it will not recover from deformation the way rubber does, so it is used as a machined component, a seal jacket energized by a spring, or a back-up ring rather than as a compressed O-ring. Moss Seal supplies virgin PTFE along with filled grades using glass, carbon, graphite, bronze, and moly to raise compressive strength, cut cold flow, and improve wear life. Typical uses include spring-energized seal jackets, back-up rings, wear bands, valve seats, and chemically aggressive or high-purity service.