Permanently charged electrostatic filter effectively captures particles as small as 0.1 micron in size from the air that passes through filter. 6 filter packs per master carton. The BestAir filter has 2 different filters that the air is passed through. * Filter 1 is a Pre-filter - It removes large dust particles, lint, and hair from the dirty air. It also captures most particles as small as .1 microns from the air * Filter 2 is the Activated Charcoal Filter - It adsorbs and helps eliminate cooking odors, musty air, tobacco odors and pet related odors as it freshens the air. Air filter fits Hunter models 30100, 30110, 30125, 30140, 30150, 30165, 37125 (30910) (30925)