SureFire's U2 Ultra is a variable power flashlight with a high-brightness LED controlled by a microprocessor that allows the user to dial six different levels of light from 2 to 80 lumens. The Ultra produces a very low output, long-lasting beam or a far-reaching, intense beam, all from a 5-watt LED. The user simply turns the power selector ring to six preset levels of light output, from dim to bright. The runtime on the Ultra varies depending on the amount of light selected. On its lowest 2 lumen setting, the Ultra runs for 40 hours.