A flat washer is a fastener that looks like a flat disk with a smooth cylindrical hole in the middle, the diameter of which is slightly larger than the diameter of the metric product with which it is used. It is made of steel with a hardness of 140, 200, 300 HV.

DIN 125 is used to increase the clamping area for various types of connections, reduce pressure on the surface of the connecting materials, and reduce friction between the nut and the surface of the part when tightening. In some cases, it is also used as a spacer to increase the distance between the nut and the surface of the part (this may be necessary if the thread of the bolt or screw is damaged at the clamping point).

Material of manufacture: high-strength structural alloy steel. 

Coating: zinc-nickel silver.

Analogs of GOST 11371-78, ISO 7089.