Winix One Year Ultimate Washable Filter Cassette; (fits size 21 models plus P300, U300, 5000, 9000, 9500) 99.99% True-HEPA Filter Washable Anti-Bacterial Pre-Filter Washable AOC (Advanced Odor Control) Carbon Filter CleanCel Anti-Microbial Product Protection helps to reduce 99.9% of bacterial growth on filter. Fits WInix Air Cleaner Models: P300, WAC9500, WAC9000, WAC5000, WAC6300, WAC5500, WAC5300, and WAC5000B.