Our 4″ Carbon Filter and Fan Combos are excellent for keeping odors away in small indoor gardens. Four inch fans, while small, still pack a powerful, odor controlling punch when used properly. The carbon filters in these kits have a slim design to maximize space in your grow tent, …but still pack a powerful, odor destroying punch. 4″ Combos will work in grow tents up to about 2’x3′ in size.