Spherical Washer Bottom Washer Inside Diameter 23.2 mm Bottom Washer Outside Diameter 36 mm Bottom Washer Radius 27 mm Finish Black Oxide For Screw Size M20 Material Steel Maximum Thickness 11.7 mm Minimum Thickness 11.7 mm Pack Size Small Pack Rockwell Hardness C40 Spherical Washer Type Spherical Washer Assembly System of Measurement Metric Top Washer Inside Diameter 21 mm Top Washer Outside Diameter 36 mm 1 Pair