White Zinc-Plated DIN 80 Plain Washers M2.5M3M4M5 Flat Gasket Washer
If you are looking for the gasket used to adjust the clearance position, mainly as a foil cushion, then it is the hardware category, metal materials are also commonly used, also known as flat gasket.
GB has GB95 GB96 GB97 and other series.The specs are in there.Chemical and petrochemical industries are likely to benefit from gaskets.