Fenix ARB-L21-5000U Rechargeable 21700 BatteryThe Fenix ARBL215000U is a high capacity 21700 rechargeable Liion battery delivering 5,000 mAh of reliable power for high drain flashlights and gear. Equipped with a built in USBC charging port, you can recharge it quickly with common USBC cablesno separate charger required. Ideal for extended runtime and convenience. Safety is front and center: it features comprehensive protection circuitry (overcharge, over discharge, short circuit, and overheat