As many other reviewers have stated, there are some issues with the size of these filters. One fit perfectly, one was too a very tight fit and the last was way too small falling out of the unit unless held in place. There was also an odor for the first week to ten days; it was not horrible but definitely unpleasant as the air purifier is used in the bedroom to help with my feline allergies. Others state the odor is as bad if you purchase direct from the manufacturer, which doesn't make any sense as there was no odor upon initial use of the product, but who knows.