Helix Racing Products Hose Clamps. Available in 5/16, 3/8 and 7/16. Sold in sets of 15. Helix Hose Clamps are double wire, self tensioning and Zinc-Plated. For use with 5/16 to 7/16 (8mm -12mm) outer diameter hose. Please enter number of clamp sets and select size from the drop down menu. Sold in Sets of 15 Please Select Size From Drop Down Menu Outer Diameter: 5/16″, 3/8″ or 7/16″ Double Wire Self Tensioning Zinc Plated Made in U.S.A.