The 20X25X5 (19.75x24.25x4.75) MERV 13 Skuttle® High Efficiency Replacement Filter doesn't always improve your indoor air quality - oh, wait. Yes, it does. In fact, it's 98% efficient when it comes to capturing harmful particles like pollen, pet dander, mold spores, viruses, bacteria and more. Additionally, the pre-applied gasketing around this filter helps prevent air bypass. This means that all of that contaminated air is being forced through the highly efficient filtrations media where it will remove those particles you do not want to be inhaling on a daily basis. So, if you want to improve your indoor air quality substantially, order the 20X25X5 (19.75x24.25x4.75) MERV 13 Skuttle® High Efficiency Replacement Filter.