Copper washer - sealing washer CU (copper) sealing washer CU (copper washer) refers to an all-metal copper seal designed for the highest pressure class where a maximum sealing effect is achieved through metal-metal contact. by the external diameter of the sealing washer (washer) × the internal diameter of the sealing washer (washer) × the thickness of the sealing washer (washer) Copper washer - sealing washer CU withstand operating temperatures within the range of: -40 to +700 °C. sealing washers are used to a greater extent in chemical facilities for the connection of fittings in pipes as sealing washers under screw connection sockets, etc.