Inner Diameter (mm): 36.7 Washer Type: Flat Outside Diameter (mm): 42 Inside Diameter (mm): 11 Outer Diameter (mm): 66 Thickness (mm): 2.5 Fits Bolt Sizes (mm): M33 Coating: Zinc Phosphate + Oil offers corrosion protection up to the point of assembly (recommend painting for external applications). Salt spray resistance of 72 hours to red rust. Coating color - dark grey to black. Material: Hardened Steel Material Description: Hardened Steel