SLN BMW S58 M3 G80 M4 G82 & X3M X4M LCI 4.0" Single Mid Pipe with Under-BraceSLN Performance G8x Series 4" Single Mid pipe with extended underbrace Welcome to the SLN 4" S58 Single Mid Pipe for the G8x platform. This is the largest bore mid pipe on the market with a true single pipe design. The quality and fitment of this product is truly world class. Features Significant power gain True 4" Single Mid Pipe Design Extended under brace Much deeper exhaust tone and reduced rasp which is typical of the S58 100% TIG welded Highest