Amazon.com: AprilAire 310 Replacement Filter for AprilAire Whole House Air Purifiers - MERV 11, Clean Air & Dust, 20x20x4 Air Filter (Pack of 1) : Everything Else
Whole House Air Purifiers | Polar HVAC | Chicago, IL & Suburbs
BestAir 16-in W x 28-in L x 4-in 13 MERV Electrostatic Pleated Air Filter in the Air Filters department at Lowes.com