Bright Eyes AAA Battery Holder Replacement - Rechargeable Flashlight Batteries With USB Head - For Bike Lights, Basic Handheld Flashlights - Stop Wasting And Start Saving Money - 18650, 3.7v Easily charge using any USB Port with brand new inline charging technology. 1300mAh so you have the power you need to keep your flashlight going. 3.7v, 18650 lithium ion battery comparable to Tenergy, Ultrafire, Trustfire and other brands but with a BIG difference - a built-in charger so you don't have to worry about losing the charger. Stop wasting money on AAA batteries for your AAA battery holder - replace the entire holder with this USB rechargeable flashlight battery plus the included battery chamber extender. Li ion battery 3.7v charges fully in just under 2 hours so you can be on your way quickly. Intelligent and safe overcharging protection is built in so you have one less thing to worry about. 18650 rechargeable USB battery size is compatible with most household and outdoor handheld flashlights giving you many uses for this battery.