Sq Washer for M12 Bolt 16 ID 50 Wd 6 Thk, Dimensional Standards AMPG 2017 SQ.01, Material Steel, Material Grade/Class Case Hardened, Finish Galvanized, For Screw Size M12, Inside Diameter 16 mm, Outside Diameter Not Applicable, Maximum Thickness 6 mm, System of Measurement Metric, Minimum Thickness 6 mm, Made in North America Made in North America, Material Quality Standards ASTM A108