When choosing tubing there are three major types to consider (from right to left); hot rolled electric welded (HREW) mild steel, drawn over mandrel (DOM) 1020, or 1026 mild steel, and 4130 chromoly. Most tubing starts as flat sheet steel that is then rolled and formed into a tube and the seam is welded. HREW leaves the seam visible, whereas DOM is then drawn over a mandrel in a colder state which work-hardens the material, and makes it tougher. Chromoly is actually an alloy of steel designed for the aircraft industry that uses chromium and molybdenum to form a extremely tough material. Unfortunately this equates in a material that costs roughly twice as much as HREW and 50 percent more than DOM. A common misconception is that chromoly is lighter than mild steel, which isn't true; however it is true that a thinner-wall chromoly has some of the same strength characteristics as thicker mild steel.