I bought these for a commercial furnace for my Daughter Lets face it a 20 x 24 does not fit BUT if you look at the "actual size" They were 19. 5 x 23. 5 PERFECT fit. We had been having to squish the previous ones in these went right in! THank you
Previously bought the MERV 8 and had no problem. Upgraded to the MERV 11 and now I get a whistle when the system turns on. Trying to return this product.