"3.5mm Audio Extension Cable" Connect your Apple iPhone 4 to any 3.5 mm stereo or receiver and output your favorite music and podcasts. If your vehicle's stereo has an aux-in port, then use the Straight 3.5 mm Stereo Audio Aux Cable to listen to MP3s or internet radio from your cell phone, PDA, or MP3 player in your car. Buy the Straight 3.5 mm Stereo Audio Aux Cable if you need a male to male 3.5 mm connection for audio output.