The Fenix ARB-L21-5000U is a high-capacity 21700 rechargeable Li-ion battery delivering 5,000 mAh of reliable power for high-drain flashlights and gear. Equipped with a built-in USB-C charging port, you can recharge it quickly with common USB-C cables—no 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 protection), as well as pressure relief vents for safe energy release. The button-top design ensures compatibility with a wide range of devices. Rated for 500 charge cycles, it maintains dependable performance over time. Key Specifications: Capacity: 5,000 mAh, Nominal Voltage: 3.6 V Charge Rate: USB-C port, up to 5 A max (standard 1–2 A recommended) Output: Up to 8 A discharge Safety Features: Multi-layer protection circuitry, pressure relief vents Longevity: Up to 500 full charge cycles Design: Button-top format, 73 mm long, ~21.6 mm diameter, ~72 g Warranty: 12-month manufacturer coverage A robust and convenient power solution—perfect for tactical flashlights, headlamps, outdoor gear, and emergency devices. Shipping Note: Lithium ion batteries are considered "dangerous goods" per US transportation regulations and can often only be transported via ground shipment. Orders containing loose batteries will typically take much longer than predicted to be delivered. Delivery times of 14+ days are not uncommon.