The Police Security Twin Power flashlight is a new, patent-pending design that improves on traditional Dual Power flashlights. It uses just one cartridge that holds a built-in rechargeable 10850 battery and 4 AAA batteries as backup. You can easily switch between the rechargeable battery and alkaline batteries with a button, so you’ll always have light. Battery level indicators let you know when power is running low, ensuring you’re never left in the dark.