I have a xtrasun 430 Watt HPS ballast. The grow store included a Solar NRG. (400 Watt HPS to MH conversion) After 3 months of using the bulb we moved. The bulb worked for 2 days at the new house, and then went to just a blue arc. The move may have negatively affected it, but it could have been the ballast. I've heard they are nearly identical components, but those slight differences affect it.