This middle exhaust itself removes the hydro-formed factory center section from the secondary catalysts back to the axle back, including both resonators, and replaces it with larger 3-inch T304 stainless steel tubing for freer flowing capabilities. In place of the forward factory resonator, Dinan incorporates a beautifully crafted X-pipe made from mandrel-bent tubing for minimum restriction, unlike stamped X-pipes which are commonplace in the market. This hand-made 'X' is not only the focal point of the system in terms of aesthetics but also the star when it comes to the effects on the sound. Promoting even flow to both banks of tips, the 'X' removes unwanted nuances in sound caused by uneven exhaust flow that is present in the stock system. Along with the inherent benefit of increased volume by removal of the resonators, the Dinan X-Pipe for the G8x M3/M4 produces a louder, smoother, and fuller exhaust note that will deliver smiles time and time again.