It's a challenge to develop an aftermarket exhaust for the great 911. The Akrapovic engineers have prepared a superb system with a dual nature. By using the optional Akrapovic sound kit, the driver can fully control the exhaust valves, which are controlled by the car’s electronics if no optional part is used. When the valves are closed, the 911 sounds deeper than stock, but not louder. When the valves are open, expect a completely opposite, pure racing sound, with adrenaline-pumping bangs. Keeping the drone effect away was one of the main tasks. The Slip-On is made of special heat-resistant durable titanium alloy, with computer-designed pre mufflers, main mufflers, and pipes to deliver more power, more torque, weight reduction, and improved throttle response.