This product is BT car charger mp3 player for vehicle with built-in Microphone. Adapting professional-grade high-performance BT Module, built-in mp3/wma decoder chip make it capable of playing the music flies in u disk, firing into the car stereo via wireless. Besides, during the BT connecting ,play the phone's music and FM transmitter to Car Audio, perfect ,as calling incoming automatically switches to the speeaker's state, call end then automatically back the music player. So you do not do any modifications, easily enjoying the music and handsfree phone calls while you are driving.Note: This item is not only support BT Handsfree phone Calling but also BT Stereo Music playing!Rated operating voltage: 12VCar Charger for most mobile phonesWorking voltage limits: 9-26VUSB output: 5V/2ASupport play format: MP3 WMASNR: >60dBDistortion: