By using Donaldsons PowerCore Filtration technology submicron contaminants load on the surface rather than collecting in the depth of the filter. This boosts efficiency and increases performance on your aftermarket air intake system. The filter media wont deteriorate as easily as traditional cotton/gauze filters. Plus its water resistant so getting wet wont ruin your air flow or cause a decrease in performance. This is why we **our replacement air filters for 4 years or 100000 miles in urban conditions whichever comes first.