Infra-red flashlight. Uses 1 cr123a battery and sending 8 batteries with. Pen in picture is for size comparison. As with any IR equipment you can't tell if it's on and working without an IR camera as our eyes cannot see Infra-red. In the dark you can see a small red glow if it's on. I have tried it out with IR binoculars. Not powerful enough to see out there 100 feet but can spot movement in closer situations. 308-340-1684