The Fenix ARB-L21-5500 is a high-performance 5500mAh rechargeable 21700 Li-ion battery that packs more capacity into the same compact size, for longer runtimes in your Fenix lights. It delivers up to 10A of output current with stable, low-temperature discharge to help prevent overheating. Protection circuits in the anode guard against overcharge, over-discharge, short circuit, and overheating, backed by three sets of overheat protection: a pressure relief valve, a separate microporous layer, and a PTC cathodal block. It is rated for 500 charge cycles and keeps up to 75% of its original capacity after 500 full cycles when properly maintained. Compatible with the TK21R, HT18R V2.0, HT32R, PD40R V3.0, PD36R V2.0, and other Fenix lights that use a 21700 battery. Charge it in the light (if it has built-in charging) or with a Fenix ARE-X1 V2.0, ARE-D2, ARE-D1, ARE-A2, or ARE-A4 charger; this battery does not have its own USB port (see the ARB-L21-5500U for a USB-C version). Price is for one battery. Shipping note: Lithium-ion batteries are classified as dangerous goods under US transportation rules and usually ship by ground only, so orders containing loose batteries often take longer to arrive than the standard estimate. Delivery times of 14+ days are common.