High-quality steel, this flat washer is zinc plated alloy steel which is one of the highest forms of corrosion-resistant steel Washer that you can depend on, very strong and is great for both indoor and outdoor use The steel is superior to regular steel and has great anti-corrosion properties Great to keep around, metal steel hardware is great to have around for use in wood and wet environments Metal steel washer is 100% strong, corrosion resistant and will support all of your projects Flat washers you can trust to prevent pull through, offers a flat bearing surface that distributes the weight ensuring a secure hold