Police Security Twin Power flashlight - a groundbreaking, patent-pending technology that redefines traditional dual power flashlights. Unlike dual power, which requires two separate battery cartridges, the Twin Power flashlight operates seamlessly with an S cartridge. The cartridge holds a built-in 10850 rechargeable battery for primary power and 4 AAA alkaline batteries for backup. With this innovative design, you'll never face the dilemma of drained power.