Spherical Washer Bottom Washer Inside Diameter 9.6 mm Bottom Washer Outside Diameter 17 mm Bottom Washer Radius 12 mm Finish Black Oxide For Screw Size M8 Material Steel Maximum Thickness 5.6 mm Minimum Thickness 5.6 mm Pack Size Small Pack Rockwell Hardness C40 Spherical Washer Type Spherical Washer Assembly System of Measurement Metric Top Washer Inside Diameter 8.4 mm Top Washer Outside Diameter 17 mm 1 Pair