CD Changers Car delivers CD-quality sound directly into the factory sound system via the CD changer port, without the loss of sound quality that occurs with existing cassette and FM transmitter solutions. Directly connect to your car radio by a vehicle specific cable harness, and directly control from car stereo panel or steering wheel, user only need a SD card or USB disk, then you can enjoy the digital music (MP3/WMA) what you like in your car, Because you can download the music that you like from internet put into SD card or USB disk, these music could be edited and played freely. And there also is Aux input for external audio sources, Auxiliary devices such as MP3 players, Portable DVD players, Minidisk Player, handheld gaming systems, notebook computers and IPHONE can be added to the OEM radio while delivering optimum sound quality.