Royal Wire's single wire hooks are made out of 3/8" diameter basic steel & then zinc plated to guard against rust & corrosion. The Cement Block Hooks fit over a standard cement block. Recommended usage with other Royal Wire products: 3-Tier Bridle rack, Main Frame, Hat Can Holder & 3-Tier Wall Basket Unit. This hook is 15" long. Please note- sold in sets of six (6) only.