They are made for a fixture that has multiple lighting intensity setting, ive got one in my house(not for growing, it was just a cool looking lamp i found at a garage sale) click one would use 13w, click 2 26w, click 3 30w in my case. You could technically use it in a normal fixture, but it will operate at its lowest setting, 13w which isnt worth using, get at least 26w bulbs, youll need like 40 of the 13w to get a good smaller serious grow going*well, as serious as a grow using 13w cfls can get*.