The outside diameter conforms to USS standards and is 36% larger than standard hardened washers for greater holding power. A smaller inside diameter conforms to SAE standards, which gives a more precise fit on bolts and nuts.
USAE washers are up to 37% thicker than standard offerings. They are mild steel, case hardened to 60 HRc, with a black-oxide finish. Bolt size is stamped on each washer for easy identification. Washers come in bolt sizes 0.25 to 1 in. and held to tolerances of M0.010 in. All are made in the USA.