Spherical Washer Steel Black Oxide Finish Fits Bolt Sizes M8 Male ID 8.4mm Female ID 9.6mm Outside Dia 17mm Thickness 5.6mm Thickness Tolerance +/-0.2mm Radius 12mm B68 Rockwell Hardness Used To Compensate For Uneven Surfaces Includes 1 Male Washer and 1 Female Washer Pair