ASTM F436 Type 1 Plain Finish Hardened Steel Round Structural Flat Washers. These carbon steel heat treated round washers are specified for use with A325 and A490 Structural Bolts. Their high strength and hardness also makes them ideal for general purpose use with Grade 8 and Grade 5 Cap Screws, as well as with fasteners meeting ASTM specs A449, A354, A193, F1554 and whenever specified as needed. Dimensions are comparable to the SAE Flat Washers with the ASTM F436 Structural washers typically having a slightly greater thickness within their listed Min/Max tolerance range. Washers are stamped to indicate the manufacturer ID and supplied plain/uncoated with a light protective oil finish.