Our XL purifier filter: The only filter you will be changing over the next 2-3 years! It also comes with our two stage M-class pre-filter! The pre-filter (which captures particles as small as 0.3 micron) collects up to 99.75% of particles and costs ONLY $3.95. The next three filters contained within the polymer frame are able to capture pollutants down to the molecule- 0.0007 diameter. One of the three filters is carbon based with ½” of GAC, with 50x more activated carbon than typical OEM pre-filter, therefore extending the life expectancy 4-8x longer.