Enjoy your music on the road even if your car doesn’t have an aux port. TuneCast In-Car 3.5mm to FM Transmitter uses FM radio to play your music through your car stereo. Connect the 3.5mm headphone jack to your smartphone and TuneCast transmits your music from your phone to your car’s FM radio. A powered USB-A port charges your phone as you go, to keep the music playing all-journey long.