Gavita makes the perfect horticultural optical system. They engineered the reflector optics and built them into the lamp. Then they perfectly aligned the arc-tube to maximize lumen output at an astounding 95% efficiency. Because the reflector is on the inside of the glass, there is no need for assembly, and the reflective material never needs cleaning. Works with any standard High Pressure Sodium ballast. Produces 95,000 Lumens.