Are you looking for a 20x20x2 filter or any other specific size? Every fall when you start your heating system, you probably want to replace your filter. It's the right thing to do. Your heating device, not only makes your indoor more comfortable, it also removes contaminants from your indoor air.A dirty filter can decrease the performance of your device, cause damage or even break your heating system. And obviously, it won't clean the air you're breathing. Have a look at your filter, if it's covered with grey dust; remplace it as soon as possible.