3M Filtrete Ultimate filters are 93% effective at capturing large particles like Pollen, Pet Dander and Dust Mite debris from the air that passes through the filter. They also remove much smaller particles, such as smoke, household dust, bacteria and particles that can carry bacteria and tobacco smoke odors. These 3M Filtrete Ultimate furnace filters have a 3M performance rating of 1900, The Performance Rating is a relative measure of a filter's efficiency at capturing airborne particles between 0.3 and 1 micron in size. Equivalent to a MERV 12 filter.