I would not go with anything rated below the CFM of the fan. You may dial it back to 55 CFM but you may find that that does not meet your needs and that you have to run it at 75 CFM in which case the filter will not be able to keep up. The 38 special might be overkill. In my case I can not afford failure. I periodically have a room full of lawyers above my grow room so I'm spending a little extra cash for a little piece of mind!
bigsby Reviewed by bigsby on . Can Filters I had a wicked odor problem with my first grow, which I just finished up a few weeks ago. I have my second batch of plants going in a grow tent in my closet right now. They are just now starting to put off a little smell. I already bought a 4" inline fan. I am just looking for a filter now. From everything I've read Can filters sound like they are the best. I can't risk getting caught so I guess I need to shell out the money for one. If I'm not mistaken they have two different 4" filters and Rating: 5