GE, MVR1000/U, 1000W, Quartz Metal Halide Light Bulb, BT56 Bulb Shape, Mogul Base, 100,000 Lumens Horizontal Or 108,000 Vertical, Universal Burn Position, 11,000 Horizontal Or 15,000 Vertical Hours, 15.37" Length, 4,000 Kelvins Color Temperature, Requires Separate Ballast, Boxed.