I ordered these for the first time and was excited I could buy in bulk. When I went to install it, however, it seemed less than 4" in depth and it was because when I measured it against the one I pulled out which was also 4" deep, the Filterbuy one was not as thick. I think it will still work fine, but there is now a gap in where the filter sits.
Ordered 30x36x2 by your chart they were supposed to be 29 1/2x35 1/2x1 1/2 they measured 29 7/8 x36x2 I had to crush the filter to get it in the furnace if it had been built as stated it would have fit fine