Review on GermGuardian FLT5000 Carbon Filter for AC5000 Series Air Purifier - 4 Pack by Kevin Webb

These are basically the cheapest quality pre-filters you can buy. I would not recommend them. They are VERY porous. They only take the biggest items like dog/cat fur, absolutely NOTHING the smaller stuff, so almost ALL filtration comes from the filter itself, which is a lot more expensive. I have 2 GermGuardian AC5350B filter machines and the manufacturer recommends changing the very expensive main filter every 6 months. I would say that with good dense pre-filters this is "overkill", but if you use those pre-filters and even change them every month, I would still say that you should probably change the main filter every 6 or even 5 months. . They're practically useless. And they're not worth returning for $18, so I guess I'll just leave them in storage to use in case I run out of ALL my pre-filters or find a way to "remap" them for something else. . I think they're better than nothing, but not much better than nothing. In comparison, the pre-filters that come with the "White Kaiman Premium True HEPA C Air Filter Replacement with Carbon Pre-Filters" are VERY EXCELLENT and what you should expect from the quality of the pre-filter. If you need pre-filters, you'll probably need new filters as well, and white Kalman filters are around $2/$40 with 4 pre-filters. So just spend the extra $20 and get 2 great filters along with 4 really good pre-filters.