Money-saving - no need to buy batteries Features:1) Mechanical flywheel generator2) Generate light anywhere, anytime with no power source required3) 2 high bright LEDs4) Money-saving - no need to buy batteries5) Environmentally friendly6) In normal status, rotate 120 turns/min, it can be used 15-20 minutes for three LEDs lighting7) Battery voltage: 3.6V, capacity: 120mAh