This 150mm 4 Watt T5 Germicidal Fluorescent lamp with a double ended G5 base is an energy efficient UVC (germicidal) bulb used in water and air disinfection units to aid with the deactivation of bacteria, viruses and other micro-organisms. Common applications are pond filtering and disinfection of drinking water. Warning; do not look directly at this light source as UVC radiation is harmful to the human eye.