5/16-18 x 2-1/2 Inch x 3-3/16 Inch Zinc Plated Low Carbon Steel U-Bolt With 2 Nuts and PlateU bolts support heavy objects from ceilings, walls, and poles. They are stronger than routing clamps and hangers and are corrosion resistant if made of galvanized steel or coated with zinc. Other types of U bolts are made of aluminum for light duty lifting, while different grades of stainless steel U bolts are also resistant to chemicals. U bolts are fastened with nuts for a tight connection.