This Axle-Back system is equipped with NPP valves. Optional system are listed below. BORLA Cat-Back and 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 BORLA Sound of Power respected by motoring enthusiasts everywhere. Each system is built from premium 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-controlled CNC manufacturing ensures an accurate fit. *** BORLA's C7 Corvette Axle-Back exhaust systems are covered under our Million-Mile Warranty for non-moving parts, the exhaust valves are warrantied for 3 years. Failures of original equipment AFM and NPP actuators are Not covered by the BORLA warranty***