True HEPA filtration removes up to 99.97% of airborne particles as small as 0.3 microns in size including smoke, dust, pollen, pet dander, mold spores and dust mite debris Replaces Honeywell HRF-R1 Recommended to replace every twelve (12) months, or more often in harsh environments, for maximum efficiency Approximate Dimensions: 6 1/2 x 10 1/4 x 1 1/2 inches Filter-Monster branded true HEPA replacement for Honeywell Filter R (HRF-R1) removes smoke, dust, pollen, pet dander, mold spores, and dust mite debris from the air.