The all new NiMH rechargeable battery pack for the C4 eLED L2 helps boost the light's max lumens up to 1000. This battery pack is airline-safe, and will last up to ten years with proper care. Please note that this NiMH battery pack will only work with the C4 eLED L2. This product is not compatible with the older C4 eLED L1 lights.