Rostra (250-7500-GM2) Factory-Style Bluetooth Switch Custom-fit and vehicle-specific wiring harnesses included in everyBluetoothkit makes for quick and easy installations normally involving no cutting or splicing of existing vehicle wiring Full Duplex Digital Signal Processing of audio by every Bluetoothsystem means you are assured the very best sound quality throughout every phone call or every streamed song Utilizing the internal memory in everyBluetoothmodule allows for the memorization of up to 5 different cellular phones; Extra phones can be added in just a few short steps, if needed Phone calls already in progress are transferred between the Bluetoothmodule and your cell phone seamlessly when your vehicle's ignition is turned on or off With the single-button volume control built into everyBluetoothcontrol switch, the audio playing over your vehicle's speakers is centralized, easy to find and easy to use