I have a few portable whole-house air purifiers in our home and they both take hepa air filters. When the hepa air filters were used up I went to buy new a singles and I was quite shocked at high priced that they were! They cost almost half the cost of the actual portable whole-house air purifiers. If I had known this when I bought the whole-house air purifiers I absolutely would have went with another brand that did not have hepa air filters. With these 2 portable whole-house air purifiers that i have no other air filter but the hepa brand air filters will particularly fit with them. They are custom for this identifiable portable whole-house air purifier. What a way to make continuous money! I bet hepa has some kind of deal with the maker of the portable whole-house air purifier. I decided that I have no option but to have to go and buy these entirely high priced hepa air filters for the portable whole-house air purifiers. I recognize I am going to look into buying a odd brand of portable air purification proposal that will allow myself and others to buy cheaper air filters when they run out. This corporation with the hepa air filters being the only air filters that will work inside it particularly to myself and others sounds like a money making scheme; Like I said, I wish I would have known this before hand and I would have went a odd direction. If I keep buying these extravagant hepa air filters for the portable whole-house air purifiers, in time I could absolutely just invest in a whole home whole-house air purifier!