Please Note! Replacement Filter Only - Does NOT Include Housing Rated Air Flow - 1800 CFM Nominal Width 21" Actual Width 20-3/4" Nominal Length 21" Actual Length 20-3/4" Nominal Thickness 5" Actual Thickness 4-3/8" Pressure Drop at 800 CFM (in. W.C.): 0.090 Pressure Drop at 1000 CFM (in. W.C.): 0.110 Pressure Drop at 1200 CFM (in. W.C.): 0.150 Pressure Drop at 1400 CFM (in. W.C.): 0.190 Pressure Drop at 1600 CFM (in. W.C.): 0.240 Pressure Drop at 1800 CFM (in. W.C.): 0.290 Fits Model [*]XHF-E21 Media Air Cleaner Housing MERV 8 Rating Protech 540042 Replaces: PD540012 540012S 540018
