Sealing washers are flat disk-shaped rings, usually metallic, with a rectangular cross section. Commonly sealing washers are made from annealed Copper (annealing treatments soften the washers), Aluminium and Fibre, however, they can also come in a wide range of materials, such as steel, stainless steel, brass, bronze, POM and PTFE. Used to ensure a reliable static seal in a variety of applications, sealing washers can be found in hydraulic connections, fittings, couplings, fuel and other automotive and plumbing systems. Annealed sealing washers are generally softer and more ductile creating a tight seal between the fittings when tightened, moreover, because of the softer contact surfaces, annealed sealing washers are less likely to damage the housing or fastener. Copper and aluminium sealing washers are available from stock in BSP and Metric sizes, according to the DIN 7603A and DIN 125A standards.