Fortune BL-A7 Portable Black Light, 6.5" Length x 1.6" Width 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 Attached strap can be looped around hand or wrist for carrying Measures 6.5" long and 1.6" wide Requires 4AA batteries (sold separately)