HTG supply sells package deals.........if you buy cheap, you get cheap with shitty results. Buy a decent unit and then u can forget about it. And yes, for it to be effective, match up the fans CFM with the recommended CFM on the filter.
i bought a cheap carbon filter from ebay [£17.50 for a 100mm filter] & it works fine as i tapped my extract from my growroom into my bathroom extract & was getting smells in my bathroom but seems to be fine now, the mrs isnt moaning anymore anyway!! how long the filter will last tho is another matter thought i would try it tho
I bought a wolfnado fan filter kit from www.3ch.co.uk. it's a 110mm dual speed fan, I use the fan on half speed=280cfm. Full speed is 590cfm. Cost me £89 and I don't get a smell at all until I'm right outside the tent.