okay thanks for your help. It seems odd that they would offer these HPS bulbs with standard household base size if you can't use them in a standard household lamp, but oh well. I think I'll just stick with flurosescents this time around and just get very high wattage bulbs. For two plants, five 105watt CF bulbs should provide enough light, I would think. That would total 34,500 lumens for two plants in that space. Sound about right? Thanks again.