The .219-.438 MS27183 Military Flat Washer Cadmium is a thin, disc-shaped metal washer with a 0.219-inch inner diameter and a 0.438-inch outer diameter. It is made of cadmium-plated steel and has a thickness of 0.025 inches. The washer is used to distribute the load of a bolt or screw over a larger surface area, preventing damage to the material being fastened. It is commonly used in military applications, such as aircraft and vehicles, due to its durability and resistance to corrosion.