Allows you to play CD, MP3 or MD players through your car"s cassette deck * Inexpensive way to listen to your digital music through your car speakers * Plugs directly into your portable player * Powered by your car"s electrical system * If you have auto-reverse on your cassette player and there is no way to disable it, this product will not work. There is a warning on the back of the package that says you have to disable auto-reverse.