Borla 16-24 Infinity Q50 (Auto V6) ATAK Cat Back - 4.5in Carbon Fiber Black Anodized TipThis 2. 5" diameter True Dual BORLA Cat Back system was designed specifically for the Q50. It features an internal H Pipe inside the front muffler and Borla's patented Polyphonic Harmonizer technology for increased performance and improved sound. BORLA'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