C21 Bluetooth FM Transmitter Hands-free Call U-Disk TF Music Player Car MP3 Dual USB Charger with Colorful Light. This car charger is multifunctional, it has Bluetooth function and can be connected with your mobile phone to play any music you like. The operation of this car charger is very simple, you can answer or hang up a call with just one button, and can adjust the volume and frequency.