The optional Akrapovič Sound Kit enables owners of selected Akrapovič car exhausts to control the sound of the system from the cockpit of their machine. Using Akrapovič 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.Fitment notice: Akrapovič Sound Kit is mandatory part needed for mounting the Akrapovič exhaust system (slip-on, link pipe set and diffuser) to Porsche Carrera 991.2 models, equipped with non sport standard systems without valves. In case the vehicle is equipped with non sport system with valves, then the Sound Kit is not needed. Please read the instructions carefully before the start of the installation.Pictures are symbolic.