This flashlight comes with a high intensity krypton gas lamp for optimum brilliance and extended range. With a twist of the flashlight head, you can change the beam from spot to flood, positioning the light where you need it most. It's anodized inside and out for improved corrosion resistance and durability, with a self-cleaning switch that virtually eliminates oxidation. The high grade O-rings at each opening ensure resistance to water and shock while the low resistance circuitry allows a more efficient use of the batteries. there's an extra lamp in the tail cap to keep you out of the shadows, and this flashlight is serially numbered for identification purposes. MagLite 6-Cell D Hang Pack S6D016