Acetal (polyoxymethylene, POM) is a stiff, dimensionally stable engineering thermoplastic with low moisture absorption, good machinability, and excellent fatigue and wear resistance. Where nylon swells in service, acetal holds its dimensions, which makes it the better choice for close-tolerance parts and precision components. Moss Seal supplies both homopolymer and copolymer grades, the latter offering better resistance to hot water and alkaline media. Typical uses include back-up rings, wear rings, bushings, rollers, valve components, and machined parts in hydraulic and industrial equipment. Acetal is attacked by strong acids and oxidising agents and is limited to around 180°F (82°C) continuous service.