DESCRIPTION - Black Luster® Steel Acorn Nuts 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*. Acorn Nuts are also known as crown hex nuts, blind nuts, cap nuts or domed cap nuts. Acorn Nuts provide a decorative finished appearance with a domed top to cover and protect the threads.