Wagan Handsfree Rearview Mirror provides a safe way to communicate while driving. Caller ID shows on LED display on rearview mirror. It broadcasts over the FM radio, MP3 player, or any other audio device with an audio output jack, turning them into your phone. Features built-in microphone, dual stereo loudspeaker, noise suppression, echo cancellation technology, voice dialing, last number re-dialing, and stores up to 200 entries in phone book. Mirror simply clips over the top of your existing mirror. Rechargeable 12V DC battery runs about a week between charges. Dimensions: 1.7"H x 11.2"L x 3.5"W.