ASTM F436 Washers
ASTM F436 washers have dimensions comparable to the USS plain washer, but with a smaller outside diameter, and manufactured with a higher grade of heat-treated steel. They are designed to be used with A325 and A490 structural bolts, but can also be used for general applications. Structural washers are most commonly supplied plain or with a galvanized finish. ASTM F436m is the standard specification for hardened steel metric structural washers.