Say hello to the Headphonies. These pint-size PA systems fit neatly in your pocket, ready for you to plug into your phone, laptop or MP3 player & pump out some tunes without the need for an external power source. Each one uses an internal rechargeable battery that charges via USB (Universal Serial Bus) & provides up to four hours playback. You can attach it to your keys (using the handy included lanyard) & always be ready to liven up a dull moment with a little musical therapy. After all, good things come in small packages. 3.5 mm connector wire for iPod/MP3 player & USB (Universal Serial Bus) charging wire both included. Lithium ion battery. Included keychain lanyard is removable. Speaker output: 2 W.