This 2.5" diameter BORLAÂ Cat-Backâ„¢ system contains functioning exhaust valves. The system delivers the classic S-Type sound with no drone inside the vehicle. The ehaust exits thru single 4" round mirror polished T-304 stainless steel tips on each muffler assembly for sharp appearance. BORLAÂ Cat-Backâ„¢ and Axle-Back exhaust systems feature patented straight-through and multi-core technology designed to unleash hidden horsepower. Increased exhaust velocity adds power driving excitement fuel economy and the distinctive BORLAÂSound of Power respected by motoring enthusiasts everywhere. Each system is built from premium high-quality austenitic T-304 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. Best of all BORLAÂ stands behind every system with a Million-Mile Warranty. Just what you'd expect from the world's most experienced (and most winning) exhaust brand.