Lightweight, slim and compact size Charges your MP3 Player battery or provide backup power for your MP3 Player Uses four AA-size batteries, which can fully charge your MP3 Player A on/off switch to prevent power leakage when not in use and a LED power indicator Provide power supply for your handheld anywhere you need it with just 4 AA batteries, especially for situation where it is hard to find a plug in outlet for a wall charger