S-Type™ Dual Cat-Back Exhaust System (140618) by Borla®. Muffler Sound: AGGRESSIVE SOUND. Side Exit. 2.25" Tubing. Dual Round Rolled Angle-Cut Long Tips. Tip Outlet Diameter: 4". Tip Length: 12". When you want the best performing, best sounding, and highest quality exhaust system, you want Borla Exhaust. Borla straight-through mufflers and mandrel-bent exhaust tubes are custom tuned to deliver the most horsepower possible, with a throaty, aggressive sound during acceleration and a definite performance tone at cruise. And the quality, aircraft-grade, austenitic stainless steel construction allows Borla to back every Cat-Back system.