So, my spec house in Texas has an undersized return air side. I need to use fiberglass type filters to keep the restriction low on the system. I have been buying the home depot or lowes blue fiberglass filters. Have not had good results with them, they never get dirty. And we have two cats, so it should pick up some hair and dust. Lowes stopped carrying my size, so I started trying several models from Amazon and Ebay. I could not find a filter that fit the housing properly, it is mounted upside down in a ceiling of my hallway. The AC/Furnace sits in the attic mounted horizontally. Anyways, I have found a disposable filter that works well. The brand is Glasfloss Industries. They just call it a disposable filter. http://www.glasfloss.com/disposable-panel-filters/ I have had very good results with this filter. Very little restriction on the system, which runs a lot in the Texas summer. Also improved airflow through the vents, which means that the house gets cooler faster. I can feel the difference of air blowing through the vents. Probably I get lower utility bills as compared to a panel type filter. Not confirmed though. I can confirm that my electric bill was 40 percent less than this time last year. Many other improvements were done such as new doors, solar screens, and caulking/painting the whole exterior of the house. Filter probably has very little to do with this. So, I purchase a case of these GlasFloss filters for about 30 bucks on Amazon. During the heat of the summer, I replace twice a month, during the rest of the year once a month. Every time I change the filter it is DIRTY. I clean the housing with a feather duster, and suck all the dust out, then replace the filter. I will continue to buy this brand of filters. I'm very disappointed in Lowes and Home Depot. They are moving to panel filters pretty much only, and a few fiberglass filters. Many older AC units were designed for fiberglass, and a restrictive panel element is choking them. I see people in the stores buying $15 each panel filters, it is just funny to me. If you want to clean the air in your house, buy a media cleaner, but your AC system is not cleaning the air in your home.