ARB-L21-4000P is a high-capacity 21700 Li-ion rechargeable battery built for longer runtimes at higher levels. These battery allows a high output flashlight like the LR35R to have its turbo setting of 10000 lumens to maintain it’s output by maintaining higher voltage for longer periods of a batteries charge. Additional features include a protection circuit in the anode to help prevent short circuits, over charge/discharge and over heating. Pressure relief vents which expel waste gas in the rare case of an internal short circuit preventing an explosion. Battery capacity up to 4000mAh. 500 charging cycles. Important Note: THIS BATTERY IS NOT COMPATIBLE WITH 18650 FLASHLIGHTS OR OLDER STYLE CHARGERS. COMPATIBLE CHARGERS ARE THE ARE-A2, ARE-A4, ARE-D1 OR ARE-D2.