This 1 7/8 USS flat washer is made of zinc-plated steel for corrosion resistance. It is designed to be used with 1/2 bolts and has an outside diameter of 1 7/8 and a thickness of 1/8. The washer helps to distribute the load of the bolt and prevent it from pulling through the material being fastened. It is commonly used in automotive, construction, and other industrial applications.