The Belkin Backup Battery Pack keeps the music playing by letting you power your iPod device with replaceable batteries-even when your internal battery is drained. It's a great solution for long plane flights, or hikes, or for anytime you don't have access to an AC outlet. The Battery Pack uses four standard "AA" alkaline batteries that you can simply replace when the charge is gone. Discreet suction cups secure the unit to the back of your iPod, without marring your iPod's finish. In addition, the Battery Pack incorporates a charge-level indicator, so you can tell ahead of time when your batteries are running low, and never be caught without your tunes again.