Diameter: 21/32Diameter 2: 1-5/16Thickness: 3/32Material: SteelFinish: Black ChromeThread Type: SAEHardness: Grade 2Nominal Size: 5/8Type: Flat WasherBox of 4.A flat washer is a thin, usually round, plate with a hole in the middle that is normally used to distribute the load of a threaded fastener. USS flat washers have a large, wider body. SAE flat washers are machined to a tighter specification and have a smaller outside diameter.