They worked quite nicely ... with their stock bulbs. I had a good sized growroom and the heat generated by the ballasts was not a problem. The link on the reply above will be useful if your growspace is limited and heat becomes a problem. Like I said I had 2 of them and grew anywhere from 1 to 4 plants from seedling through harvest. I was very pleased with the resulting harvest with both soil and hydro. I wouldn't do more than 2 plants per light.

Later,

Helen