Spherical Washer Bottom Washer Inside Diameter 0.313 in Bottom Washer Outside Diameter 0.625 in Bottom Washer Radius 0.75 in Finish Plain For Screw Size 1/4 in 3/16 in Material Stainless Steel Material Grade/Class 18-8 Maximum Thickness 0.188 in Minimum Thickness 0.188 in Pack Size Small Pack Rockwell Hardness B83 to B95 Spherical Washer Type Spherical Washer Assembly System of Measurement Inch Top Washer Inside Diameter 0.281 in Top Washer Outside Diameter 0.625 in