18x24x4 MERV 13 Pleated AC Furnace Air Filters by Glasfloss Industries. 4 Pack

18x24x4 MERV 13 Pleated AC Furnace Air Filters. 4 Pack Actual Size: 17-1/2 x 23-1/2 x 3-3/4 | Nominal Size: 18x24x4 Filtration Rating: MERV 13. Comparable to MPR rating 1900 to 2200, or FPR 10 rating. Effectively captures and blocks small-particles such as virus carriers, bacteria, allergens, smog, smoke, lint, dust, pet dander and pollen.