I have a few portable whole-house air purifiers in my lake house plus they both take hepa air filters. When the hepa air filters were used up I went to buy current ones plus 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 truly 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 absolutely fit with them. They are custom for this unique portable whole-house air purifier. What a way to make continuous cash! 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 plus buy these genuinely high priced hepa air filters for the portable whole-house air purifiers. I suppose I am going to look into buying a weird brand of portable air purification idea that will allow me to buy cheaper air filters when they run out. This contractor with the hepa air filters being the only air filters that will toil inside it absolutely to me sounds like a cash making scheme; Like I said, I wish I would have known this before hand plus I would have went a weird direction. If I keep buying these lavish hepa air filters for the portable whole-house air purifiers, in time I could truly just invest in a whole lake house whole-house air purifier!