I recently purchased four MERV 11 filters from Filter Buy. Not only were they cheaper than the HVAC company that installed my heat pump, I also was able to get the MERV 11 ones instead of the MERV 8 ones that were originally sold to me. Thanks!
Filter's cardboard frame is smaller than retail brands...this causes filter to be too loose in wall mount holder. Air will sweep around sides of cardboard frame. All retail brand filters, with same dimensions, fit correctly in my wall holders....