Filter-Monster branded replacement filter compatible with Holmes AER1 air purifier filters (HAPF30 / HAPF300). Engineered to fit Holmes AER1 air purifier models, as well as Bionaire models BAP536 and BAP516. Replacement for Holmes HAPF300 and HAPF30 filters. True HEPA filtration removes up to 99.97 percent of airborne particles as small as 0.3 microns in size including dust, pollen, wildfire smoke, pet hair and dander, mold spores, and dust mites. Recommended to replace every twelve (12) months for maximum efficiency, or more often in harsh environments. The package contains two (2) replacement filters. Filter dimensions: 10" x 4 3/4" x 1 1/2" (Dimensions include filter body only. Including side tabs, product width is 5" instead of 4 3/4").