Fortune Products Portable Black Light Blacklight Set of 3 4AA batteries required (best with Polaroid AA batteries) Portable black light can be used to detect invisible ink, find pet stains, or perform similar tasks Contains 4-watt bulb; emits long-wave ultraviolet light at 365 nanometers Measures 6.5" long and 1.6" wide Attached strap can be looped around hand or wrist for carrying