Earth Worth 600W Electronic Digital Ballast For HPS or MH 600 Watt Grow Bulbs - Dependable and Affordable! Rated Power: 600 watts (High efficiency) Bulb Compatibility: 600 watts High Pressure Sodium Lamps OR Metal Halide Lamps Quiet Operation Reduces Operating Noise Interior Fan saves Energy and Lowers Operating Cost Specified Frequency: 50/60Hz