When you are buying air filters for your central heating and a/c plan 1 thing a lot of folks do not realize is the fact that you need to get the right fit and size for whatever it is that your air filters are inserted to. There are so several unusual shapes and sizes when it comes to air filters for central heating and air conditioners. It could be that you may need a single air filter that is smaller or appreciate my central heating and air conditioner, you need several air filters that are rather large. That is the way it constantly varies per heating and cooling set up in your home when it comes to air filters. I l gained this just a few months ago when I moved into a current lake house that had this unregular air filter set up on the central heating and air conditioner. I had never heard of having 2 giant air filters before. It goes to show how much I know. It may be because this central heating and a/c plan puts out more grime and dust than others? I have no method to tell you the truth. All I suppose is that I have to buy 2 actually giant air filters each time. Do not ask me what the dimensions are because I have them written down anywhere and I look at it every single time I need to buy more air filters for my central heating and a/c plan unit. So constantly check the size of the air filters that you may need before buying them for your Heating plus A/C unit.