the product looks like a car cigarette lighter plug and is fitted with usb and sd slots that will accept a standard usb flash drive or sd/mmc card, and it will play and transmit your mp3s to fm channels, so that user can listen the mp3 music from the car radio in full stereo. turn any usb memory drive into an mp3 player with this amazing modulator! this fantastic little device will play all your audio devices wirelessly through your car stereo system, clearly and efficiently. supporting mp3 and wma playback, cruise to all those funky tunes in the comfort of your own vehicle.