this ultra-bright led headlamp lets you choose 1 3 or 7 leds. powered by 3 "aaa" alkaline batteries (included) seven 100 000 hr. life ultra-bright white leds 50 lumens typical (7 leds) 25 lumens typical (3 leds) 9 lumens typical (1 led) runs up to 150 hrs. (single led) adjustable elastic head strap and rubber hard hat strap facecap diameter: 1.86" max width: 2.55" max depth: 2.53" including head strap and mounting plate 4.72 oz.