Fluorescent lamps are a low-pressure mercury-vapor gas-discharge lamps that uses fluorescence to produce visible light. A fluorescent lamp converts electrical energy into useful light much more efficiently than incandescent lamps. The typical luminous efficacy of fluorescent lighting systems is 50–100 lumens per watt, several times the efficacy of incandescent bulbs with comparable light output. Fluorescent lamp fixtures are more expensive than incandescent lamps because they require a ballast to regulate the current through the lamp. The T5 is featured with tubular shape and 15.875mm diameter.