Winix 115122 PlasmaWave Series Long Life Washable Filter, Size 21, carbon pre-filters(4) Includes one washable true-hepa filter and 4 Carbon filters (one year supply) True-HEPA filter can be washed up to 3 times before replacement is needed Removes 99.97% of all airborne pollutants as small as 0.3 microns Carbon filters remove odors Fits the Winix air cleaner 115122 5500