Yep, one fixture, and i mean yea they might be slightly less effective but for only another $80 bucks for the MH Conversion bulb instead of another $450 for a whole new MH 1000 watt setup... I'll go with the conversion and save that extra $270 for my ventilation and climate controls... just my two cents, unless u got money to burn then i would invest upfront in a switchable or just get a conversion bulb for HPS -> MH cause the other way (HPS conversion for MH ballast is like $195) is more expensive.