This dual 3.5" diameter split rear exit Cat-Backâ„¢ system has active exhaust valves with a dual 3" diameter rear section for the loud path and dual 2" rear section for the quiet path. The system was designed specifically for the 4.4L M8 Gran Coupe. It contains a Merge X-Pipe for increased performance and improved sound. It also features our Polyphonic Harmonizer and SwitchFireâ„¢ technology. BORLAÂ'S Polyphonic Harmonizer Technology utilizes patented units that contain pipes of different diameters and lengths to create multiple exhaust notes that harmonize to deliver a clean rich full-bodied sound. Completely eliminating the turbulent center intersection of a standard X-Pipe BORLAÂ'S patented SwitchFireâ„¢ design truly blends the combustion pulses from both sides of the engine for improved performance and a custom sound. It delivers the aggressive ATAK Sound with no drone inside the vehicle. The exhaust exits via dual 5" round carbon fiber with black anodized center tips on each tail pipe. BORLA Cat-Backâ„¢ & Axle-Back exhaust systems feature patented straight-through and multi-core technology to unleash hidden horsepower. Increased exhaust velocity adds power driving excitement fuel economy and the distinctive BORLA Sound of Power respected by motoring enthusiasts everywhere. Each system is built from premium high-quality T-304 austenitic stainless steel superior to T-400 series knockoffs (such as 409) to give you the absolute best in performance and durability. Ultra-smooth mandrel bends ensure maximum flow & power and precision computer numerical control (CNC) manufacturing ensures an accurate fit. This system gives your M8 the power and sound it deserves. Best of all BORLA stands behind every system with a Million-Mile Warranty. Just what youâ€d expect from the worldâ€s most experienced (and most winning) exhaust brand.