The Fenix ARB-L21-6000 21700 rechargeable Li-ion battery has a capacity of 6000mAh, providing the necessary voltage and power for long-lasting use and increased lumen capabilities. With the same features as other high-quality Fenix batteries, such as internal protective circuits and up to 500 charging cycles, the ARB-L21-6000 can ensure extended runtime and consistent performance. It also offers three sets of overheat protection - pressure relief, microporous, and PTC cathodal block - to maintain the battery's safety and stability. Never be without light; order a spare 21700 battery today. PRICE IS FOR ONE BATTERY Recommended for use only in compatible Fenix products purchased in 2025 or later. Compatible products: CL27R, E35R (purchased 2025 or later), HT18R, HT32, LD36R, LD45R, LR35R PRO, LR36R, PD36R V2.0, PD40R V3.0, PD45R ACE, TK17, TK21R, TK22R, TK25R, TK30R, WF25RM. NOT COMPATIBLE with the following lights: BC26R, CL26R PRO, C7, E35R (purchased prior to 2025), LR35R (original), PD36R PRO, PD36 TAC, TK16 V2.0, TK20R V2.0, WF26R, HM70R, HM71R, HM75R or any older Fenix models that utilize a 21700 battery such as the Version 1 of the PD36R. This battery is not an 18650, and it is not compatible with 18650 flashlights. COMPATIBLE CHARGERS ARE THE ARE-A2, ARE-A4, ARE-D1, OR ARE-D2. Will not work in older chargers such as the ARE-C1 and other "C Series" chargers. This is not the version of the battery with direct USB charging. 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.