The optional Akrapovi? Sound Kit enables owners of selected Akrapovi? car exhausts to control the sound of the system from the cockpit of their machine. Using Akrapovi? technology, drivers can easily switch between the quiet mode and a sportier sound. With the use of a receiver to drive the actuators that open or close the valves at the end of the exhaust system, drivers can use the Sound Remote Controller or the new smartphone app (for iOS and Android) to regulate the valves.If the car is not equipped with Porsche performance exhaust and you want to use the Akrapovic sound kit than Akrapovic sound kit P-HF1003 with Actuator set P-HF1006 has to be ordered.If the car is equipped with Porsche performance exhaust with electric valve actuators than actuator set P-HF1006 is required and the Akrapovic sound kit P-HF1003 can not be used. The valves are opened or closed with the valve button inside the car.Pictures are symbolic.