It has two headphone sized jacks on either end. It cost about $10 i think. Maybe more, I'm not sure. But you have to have an input jack on your head unit in your car that says 'aux' on it. That's it basically, a direct connection to your car stereo, but they're only in new 2005 cars and some after market head units. Be careful if you buy a new head unit because some advertise this feature, but they only have the jack in the back of the unit where only installers can reach it, okay for stuff like satelite radio, but not really useful for an mp3 player, you'd now if you had one in your car though, it looks like a headphone jack on your stereo.
A lot of posts back a couple of you recommended an auxilary cord for a cd deck in order to listen to your mp3 player through your car. What is that? I know computers but I don't know car electronics. Please help.