This is a Nextorch 18650 lithium-ion rechargeable battery for flashlights and headlamps. The 18650 is the most common rechargeable cell in modern torches, including many Nextorch models such as the oStar headlamp and several tactical and hunting lights, and it can replace a worn battery or serve as a spare for long trips and night work. We could not find the exact capacity or protection details for this Nextorch item, so please check that your flashlight takes an 18650 cell (about 18 mm across and 65 to 70 mm long) and ask us if you need the capacity before buying. Charge it in a suitable lithium-ion charger.