I use a 4" one of those homedepot ones for a 150watt HPS cool tube. It works nice, you can't even feel heat 1" from the bulb. Haven't used the bigger ones, but seems like it would work the same.

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ForgetClassC Reviewed by ForgetClassC on . closet grow!!! heat help What is your experience level? (first timer, novice, experienced...) first timer Your Equipment: .1) Type and wattage of lights. 23w cflâ??s for now .2) Distance from tops? 1 to 2 inches .3) Reflector type? lamp .4) Is there a consistent fresh air supply? There are two fans in closet no exhaust .5) Do you have an exhaust fan and a circulation fan? Just a circulation fan and a small fan .6) What are the bulb wattages, kelvin ratings, and schedule? 23watt CFL's on a 18-6 Rating: 5