no batteries needed: charging by shaking! Based on Faraday's Law of Inductance: a magnet passes back and forth between a wire coil giving charge to the flashlight' s capacitor. 1 minute of shaking generates up to 5 minutes of light. Shock and water resistant, virtually indestructible, LED with high visibility, ideal for camping, hiking, boating and general emergency situations 175 x 40 mm, 125 g