Features The most common kind of round washer, Flat Washers feature 2 flat surfaces for distributing the force/stress of a nut or bolt. They also help to reduce friction and heat during the installation of a threaded fastener. Flat Washer Type / Flat Washer Washer Basic Material / Steel System of Measurement / Inch Washer Material Grade / Low Carbon Fastener Finish / Zinc Plated Fits Bolt Sizes / 5/8 in Washer Inside Dia. / 11/16 in Washer Outside Dia. / 1 3/4 in Thickness / 0.1406 in Color / Silver Package Quantity / 50