18 x 18 x 1 (17.7 x 17.7) Filtrete Ultimate Allergen Reduction 1900 Filter by 3M

With a 1900 performance rating, no competitors 1 filter performs better. It is 26% more efficient than the Filtrete Advanced Allergen Filter. This product is 93% effective at capturing large airborne allergens, such as pollen, mold spores and dust mite debris. It also captures small particles such as smoke, smog, household dust, pet dander, bacteria and particles that can carry viruses and tobacco smoke odors. This product lasts up to 3 months.