Narrow Rim Type B Washer, Flat Washer Type Standard, Dimensional Standards ASME B18.22.1, Material Steel, Material Grade/Class Case Hardened, Finish Zinc-Plated, For Screw Size 1/2 in, Inside Diameter 0.531 in, Outside Diameter 1 in, Maximum Thickness 5/64 in, System of Measurement Inch, Minimum Thickness 1/16 in, Color Silver, Inside Diameter Tolerance +/-0.010 in, Material Quality Standards ASTM A108, Outside Diameter Tolerance +/-0.010 in, Pack Size Small Pack, Rockwell Hardness B55