Ryan, in the shop built air cleaner I had I used the cheap filter first, then a Filtrete red, then a Filtrete Ultra-allergen. It was very effective, and while I had to replace the first one fairly often I don't recall ever replacing the ultra-allergen, though I did replace the red one once....that was over a 5 year or so period. I left that in the last house we had and really wish I had taken it down and brought it with me. It was ceiling hung. These type of shop built units work so well, and are so cheap I can't understand why so many of the commercial ones are sold.