That is the way air filters work! Of course if you want to avoid having to alter the air filters you buy all together you can just check your central heating and cooling system’s air vent and air filter areas and find out the exact size of the air filters you need by measuring it all with a tape measure
If you happen to buy air filters that may not be the right size for your central heating and cooling system and they are too big, one thing you can do if you do not want to go through the hassle of returning them is to cut them, and yes, this method easily can work because I have done it a few times. Sometimes when you buy air filters for a central heating and cooling system that is in a dwelling you are renting, you may not know the exact size and try to estimate. When this happens there could be mistakes. So the one thing you can do like I said is to cut them to fit. The main thing you need to do is cover the air vent openings of your central heating and cooling system with the air filters. That is the way air filters work! Of course if you want to avoid having to alter the air filters you buy all together you can just check your central heating and cooling system’s air vent and air filter areas and find out the exact size of the air filters you need by measuring it all with a tape measure. That is what the best thing to do is if you do not want to mess with having to alter the air filters for your central heating and cooling system unit. This is what I most recently did because I was tired of having to cut the air filters to my central heating and cooling system unit when I would buy the wrong sized ones.