I've done a ton of reading on filters. It is my only real concern. I've found that Mountain Air filters get top reviews consistently. They are rated to last longer at 3 years but they also come at a premium. I'm looking at one that will fit my 340 CFM fan for $205, although I could probably find it a bit cheaper online. My preference is to buy supplies locally in cash... Can fans do well, so do Phresh. My thinking is that you will be fine with most of them. When sizing, over size rather than under size. If you under size you will have oder. If you over size the filter will last longer. You decide!