Flat Washer, Dimensional Standards AMPG 2001 FL.05, Material Steel, Material Grade/Class Case Hardened, Finish Galvanized, For Screw Size 1/2 in, Inside Diameter 0.563 in, Outside Diameter 3 in, Maximum Thickness 1/4 in, System of Measurement Inch, Minimum Thickness 1/4 in, Made in North America Made in North America, Material Quality Standards ASTM A108, Thickness Tolerance +0.005/-0.020 in