ipower 400 watt digital dimmable electronic ballast for hps mh grow light - Walmart.com
Magnetic ballast - MH/HPS lamps - GrowLab
Universal Lighting Technologies M400MLTAC4M500K Magnetic Core and Coil Ballast, Metal Halide, 400W, 120-277V: Led Household Light Bulbs: Amazon.com: Tools & Home Improvement