Promethfire Purple 9 X Cree LED Uv Flashlight Torch Mini Flash Light Led Lantern (Black) Ultraviolet flashlights are useful tools to fight the criminal element and provide security Many currencies contain a UV fluorescing strip.Used to detect fake money Checks ultraviolet inks in paper currency Checks credit cards To help find out leaks, like air conditioner leaks, oil leaks and sunroof leaks