These rear sway bar reinforcements are an upgrade for your BMW. These are necessary if you install a large aftermarket sway bar or track your car. They are CNC plasma cut from 14 gauge steel, and left raw so you can weld them in place. Welding to your rear subframe is required for this install. Make sure to remove your brake ABS/pad sensor box before welding, and also remove any paint before welding for best penetration. This is for a pair of reinforcements.