Royal Wire's single wire hooks are made out of 3/8" diameter basic steel & then zinc plated or powder coated to guard against rust & corrosion.  Recommended usage with other Royal Wire products:  3-Tier Bridle rack, Main Frame, Hat Can Holder & 3-Tier Wall Basket Unit.  All single wire hooks fit over a standard "2x4".  This hook is 15" long.   Hooks are now sold individually.