[M8(8.5mm) outer diameter 25mm thickness 1.5mm]
[M8(8.5mm) outer diameter 18mm thickness 1.2mm]
The washer has a larger outer diameter than the standard size flat washer, so it is expected to reduce the phenomenon of the nut or bolt head into the clamping material (seated recess) and stabilize the tightening surface.
Besides metal, it is also suitable for fastening FRP and wood etc.