The DIN 9021 is a standard specification from the Deutsches Institut für Normung (DIN) in Germany that outlines the requirements for large diameter washers with a smooth, flat surface. These washers are designed to distribute the load of a threaded fastener, such as a bolt or screw, over a larger area to prevent damage to the material being fastened. The standard covers washers made from materials such as steel, stainless steel, and non-ferrous metals, and specifies the dimensions and tolerances for each type. DIN 9021 washers are commonly used in construction, automotive, and machinery applications, where they play a critical role in ensuring the integrity and stability of assembled components.