Cycle Standard custom exhaust tubing is 1.75 inch diameter, 16 gauge (.063 inch thick) 1008 mild carbon steel, cold rolled, electronically welded for superior finish and quality, ready for MIG or TIG welding. Perfect for making a custom exhaust for your motorcycle or modifying an exhaust you already have, these mandrel bends are CNC bent to ensure a perfect radius and a consistent tube shape throughout the bend. The centerline radius is measured from the center point of the legs (straight sections) of the U bend. A 2 inch centerline radius would measure 4 inches across from center to center on the legs. A 2.5 inch centerline radius would measure 5 inches across, etc.