This genuine AprilAire 401 Air Filter Replacement is rated MERV 10. The 201 filtering media is a surface-loading filter. This means that its efficiency increases with usage. The 401 filter can last up to 2 years. If you run your HVAC system fan all day, every day, replace it after 12 months.
Approximately 17x 28x7.47
Aprilaire and Space-Gard: 2400
Lennox: PMAC-12C, X0444
Other Manufacturer Part Numbers: RP401, DRP401, DSG401, RES401, REP401, DPFS2400AA