Structural Flat Washer, Steel, Hot Dip Galvanized Finish, Fits Bolt Sizes 5/8 In, Inside Dia 11/16 In, Outside Dia 1 5/16 In, Thickness 0.122 to 0.177 In, Rockwell Hardness C26-45, Used For Structural Leveling, For Use With A325 and A490 Bolts, Meets/Exceeds ASTM F436, Package 50