I had a 300watt cfl bulb in closet and about 24 to 36 in out I think that's how much out it is.. Im gonna use until i can get a better setup and lights I'm gonna grow outside when I move in August..I just had these and was trying to learn to growWhat kind of led and how close? I found that they like them within 16-24 inches with my mars hydro 600 100wat actual. And I'm running them about 30 inches right now because I have another led in there. I like the cfl 6400k for early verging. I noticed adding a small 24wat 6400k cfl within 8 inches of plant really helped node spacing.