Square Nuts are four-sided with a flat bottom side and a chamfered, washer-crowned top. 18-8 ss, 316 ss, 400 series ss, Brass, Silicone Bronze, Monel, Carbon Steels, Alloy Steels, Aluminum.Zinc, Cadmium, Nickel Silver & Chrome Plating, Black Oxide, Anodize, Passivation and Heat Treating.