My filters are in the ceiling, the ones I got just a little smaller than the original ones. I have to hold it in and close the cover. The original ones stay in place. Otherwise they work perfectly.
I was forced to cut out the diamond pattern from both sides of my 12 X 12 filter because my furnace was being starved of return air. I tried the 13 to 8 Mer first but was unable to tolerate the loud noise coming from registers.
It's been busy a week, Less dust, easier breathing, thus far all is functioning as advertised. The site was easy to use, delivery was quick. If only they produced a filter for stupid . . . But where would we install it?