Material: HARDENED STEEL Washer Type: Flat Outside Diameter (mm): 32 Inside Diameter (mm): 13.5 Fits Bolt Sizes (mm): M12 Thickness (mm): 8 Material Description: Hardened Steel 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. Inner Diameter (mm): 13.5 Outer Diameter (mm): 32