I made a nice sized carbon scrubber for my 8in wind tunnel today. Took me a good 3hrs to make, and a huge mess of carbon all over the floor afterwards. I thought it would be restrictive on the fan but its not at all. Theres still the same amount of suction on the grow room door so its gota be doing its job. I'll take pic's of it tomorrow. cost me $12 in carbon, $8 in panty hose, and $7 for the end cap and other connector. So its pretty damn cheap!