Lennox X6664 MERV 10 Filter - 17" x 26" x 4" - Genuine Lennox Product Use in Lennox PureAir PCO-12C Air Cleaner MERV 10 Efficiency to capture particles as small as 0.3 microns Actual Size: 16-5/8" x 26" x 4" Replace every 6 months in normal use Genuine Lennox OEM Filter