DESCRIPTION - Black Luster® Grade 5 Steel Hex Flange Bolts 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*. Flange bolts have an attached washer-like base that covers oversized holes and distributes weight to reduce stress at the joint. These bolts can be used with a mating nut to fasten two or more parts together.