All tubes are CNC mandrel bent for optimal flow for all bends in this rod builder kit. Made from 304 stainless steel for maximum corrosion resistance. The diameter of tubes is 3-1/2" with a .065 wall thickness. Kit includes (4) 4' straight tubes, (4) 45 degree bends, (4) 90 degree bends, and (4) 180 degree bends. One expanded end on each tube in kit. We recommend the use of 308L SS welding rod. These kits are proudly made in the USA.