Shop › Exhaust Builder kit Image 1 of 1 Exhaust Builder kit $125.00 DIY Builder kit. True mandrel bends. Mild Steel. includes.1 U-Bend (180 degree)1 90 degree2 45 degree Add To Cart Added! DIY Builder kit. True mandrel bends. Mild Steel. includes.1 U-Bend (180 degree)1 90 degree2 45 degree