Comsoon Bluetooth 4.2 FM transmitter for car, wireless radio car kit with dual port car chargers the easiest way to add Bluetooth function to your car stereo system, the simplest hands-free solution to bring wireless audio to your existing car stereo and listen to your favorite songs. Safe for calling built with a high-quality microphone, totally free your hands, just press the phone call button and speak while you are driving with both hands safely. Three music play mode 1) Bluetooth connection automatically and simply paired your phone with this device via stable Bluetooth. Bluetooth sound processing a2dp, offers a comfortable stereo music playing. 2) tf card insert tf card into the slot, then automatically play and transmit the mp3/wma/wav music, 3)aux cable connect with your phone or iPod via aux cable, play your favorite music to relax your body and mind during your driving. How to adjust FM? 1) choose your radio into a blank unused FM frequency (87.5-108.0mhz), 2) adjust this FM transmitter to the same frequency: Adjust the ch+/chbutton to increase/decrease FM frequency. Aux input/output--supports aux cable connection 1)aux input function offers a second way to connect your phone or iPod with FM transmitter via aux cable, instead of Bluetooth connection, 2)aux output function offers a second way to connect FM transmitter with car audio via aux cable, instead of FM frequency match. Warranty: At Comsoon, we back you all with 1 year warranty, under 24-hour amazon email contact service and easy-to-reach, friendly technical support. Package included: 1x Bluetooth FM transmitter with dual USB ports 1x user manual.