Filter-Monster branded replacement filter kit compatible with Whirlpool Large Air Purifier models AP51030K, AP51030KB, AP45030K, APR45130L, WP500 series and WP1000 series. True HEPA filtration removes up to 99.97 percent of particles as small as 0.3 microns in size including smoke, dust, pollen, pet hair and dander, mold spores and dust mites. Carbon pre-filter reduces household odors from cooking, cleaning and pets. Also extends life of HEPA filter by capturing larger particles, before reaching HEPA filter. Recommended to replacement HEPA filter every twelve (12) months and pre-filter every three (3) months for maximum efficiency, or more often in harsh environments. Package contains one (1) replacement 1183054K HEPA filter and four (4) replacement 8171434K pre-filters.