I've been using this filter in sizes 20x30 and 20x20 for over one year and definitely see a difference. There is less dust in the house, the air is cleaner because it filters out the harmful particles in the air. It costs much more than the cardboard ones but it does its job for the price. I have a 3 year old TRANE air conditioner and want to make sure to use the best products for it and that would be FILTRETE!