Wireless FM transmission lets you enjoy your favorite MP3 music in your car, truck, boat or RV. Insert into your vehicle's 12V cigarette lighter socket. Built in FM Stereo Transmitter Module to broadcast the MP3 music to preselected radio channels. Adjustable frequency. Choose the least interfered frequency between 87.7 and 88.9 MHz on your car stereo. USB Host Control Interface to read most kinds of USB Flash Drives