Inner Diameter (mm): 8.4 Outer Diameter (mm): 20.4 Thickness (mm): 2 Fits Bolt Sizes (mm): M8 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 Washer Type: FLAT WASHER Material Description: Hardened Steel