Double Ended or DE grow lamps are more efficient, can offer an improved light spectrum and have quicker warm up & re-strike times as well as improved lumen maintenance over the lifetime of the lamp. These bulbs are more efficient and the arc tube is a little bit longer. The electricity flows from one end of the arc tube and out the other. This makes them inherently more efficient than bulbs that require electricity to travel farther less efficiently. The new bulbs produce about 15% more light than single-ended bulbs. Since the bulb is attached at both ends, the arc tube is always mounted parallel to the reflector for maximum efficiency and reflection.