Virtual Sun VS400WMB 400-Watt Magnetic Grow Light Ballast Bulb compatibility: 400 watts high pressure sodium lamps or metal halide lamps Input power is stabilized and improves efficiency of equipment Prevents fluctuations in power from hitting the bulb, causing premature burnout Working voltage - 120/240 (comes with 120v 3 prong plug) Interior fan saves energy and lowers operating cost