Mutant Media YoYo Portable Speaker with Built-In Battery, Green Portable pocket sized YoYo shape for easy carrying Expendable diagram to enhance bass sound effect Retractable 3.5mm audio jack makes it compatible with iPhones, iPods, and most MP3 players. Glow LED power indicator ring adds night time ambiance Built-in rechargeable Lithium Ion battery for extended play without other power source iPhone, iPods, & More