Diameter: 9/32Diameter 2: 5/8Thickness: 1/16Material: AluminumThread Type: SAENominal Size: 1/4Type: Flat WasherBox of 48.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.