ATAK 304 SS Cat-Back Exhaust System with Split Rear Exit (140864BC) by Borla. Exhaust System Type: Cat-Back. Exhaust Tubing Material: 304 SS. Main Tubing Diameter: 3" to 2.25". Exhaust System Sound: Aggressive / Loud. When you want the best performing, best sounding, and highest quality exhaust system, you want Borla. Borla straight-through, multi-core ATAK mufflers and mandrel-bent exhaust tubes are custom tuned to deliver the most horsepower possible, with the most aggressive sound of any Borla system. And the quality, aircraft-grade, austenitic stainless steel construction allows Borla to back every exhaust system with an unequaled million-mile warranty.