This 100W lamp fits inside a modified Sciencetech FB-QTH-3 QTH Fiber Illuminator. It has a 2-pin G5,3 socket, built-in 50mm dichroic MR-16 reflector, and has a service life of 200 hours. Please note that the Sciencetech FB-QTH-3 QTH Fiber Illuminator design needs to be modified to accommodate this 100W lamp as its voltage and working distance is slightly different than the standard 150W QTH lamp.