Air Quality Improvement: Filtration is rated H13 and removes up to 99.97% of airborne particles as small as 0.3 microns in size including dust, smoke, pollen, pet hair and dander, and more. Maintenance: Recommended to change this filter once every twelve (12) months under normal conditions, and more often under harsh air conditions. Approximate Measurements: Each filter measures 15 3/4 x 18 7/8 x 2 inches. Replacement Quantity: Each package contains one (1) replacement filter. Filter-Monster branded replacement filter Compatible with Whirlpool 1183054K filter. This filter is compatible with Whirlpool AP51030K, AP51030KB, AP45030K, APR45130L, WP500 series and WP1000 series Air Purifiers.