DESCRIPTION - Black Luster® Steel Fender Washers provide best in class decorative appearance and better corrosion resistance than black oxide and zinc plated finishes. Resistant to 1,000 hours of salt spray per ASTM B117*. Fender washers, though similar in shape to a standard washer, differ in that the outside diameter is traditionally much larger in proportion to the center hole. With this design, a fender washer can be placed under the head of a bolt or nut to help distribute forces applied when tightening.