These filters are a 1/1 copy of the original Kenmore filters but at a fraction of the price. I have aquariums and the density of the medium is of great importance when it comes to developing beneficial bacteria and filtering out debris. Vacuum filters are similar in a later feature. These particular filters are the pre-filters in the Kenmore HEPA system, on the other hand there is another filter that is similar to the filters in HVAC systems and needs to be replaced accordingly. (black part) and some cotton filler (white part), I think they are designed to keep odors out of the canister. So, 1/1 filter for a fraction of the cost, what's not to like?