its a great way to make a quick filter on the cheap without paying the markup for the trangely dimensioned filters of commercial air filter machines. You can put more or less money on the actual filters depending on what you need to filter too. I have like 6 or 7 of these going between my workplace and home. some are set up with construction dust in mind, a couple to get the smoke from outside at work which gets in when doors are left open, and the rest for pet dust.