This multipurpose flashlight lets you choose red light or white light with the flip of a switch. Red for preserving night vision while at the telescope; white for increased brightness and visibility when packing up, or for non-astronomical applications. Brightness wheel sets the desired intensity, from dim to bright. Runs on one replaceable 9-volt alkaline battery (included). Just 4-1/2" long, with 20" lanyard. Once you try the Orion DualBeam LED Astro Flashlight you'll immediately appreciate its versatility!