This S-Type II system use a special muffler design to eliminate sound frequencies that are often associated with resonance or drone. The 2.5" diameter into dual 2" Cat-Backâ„¢ system will fit vehicles with and without NPP. BORLAÂ system does NOT include NPP valves. System features dual 4" round polished T-304 stainless steel tips on each muffler. BORLAÂ 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 BORLAÂ 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. 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.