The Quasar Tubes Q-LED X CrossFade Linear Lamp 4ft is a Variable Color LED replacement for a T12 4′ fluorescent lamps. These 50 watt tubes produce 90 lumens per watt! Quasar lamps are dimmable, flicker free and 25,000 hr average life. Best of all the Quasar Tubes are rugged, built with aluminum frame and plastic front diffuser. They can operate as a single tube or ganged together for a large light source. A really neat tool is the optional Modern Studio Fluorescent Lamp Holder. Holds a single tube and has a 5/8″ diameter baby pin for mounting in a c-stand.