My furnace/AC was installed about three years ago. It uses 16" X 25" X 5" filters. The problem is when I try to find a replacement at my local home center: at Lowe's, Home Depot, (you name it), I found only 1" or 2" thick filters (mostly 3M Filtrete). I looked in many stores around my area, not just one. I also checked at my local Costco and Walmart but they have none: the associates told me that they didn't carry the filters anymore and that I may need to order them online.
So, the question is: Are 5" thick filters still in use and available? Is it an uncommon size filter? Or do the thin filters have better performance?
Additional Information: the filer that we are talking about is Honeywell FC100A1029.