Sterling Seal FI-8201-SP1x6 Purolator Hi-E 40 Extended Surface Pleated Air Filter, Mechanical MERV 8, 18" Width x 22" Height x 1" Diameter (Pack of 6) Mechanical MERV8 Filter Exceeds ASHRAE Standard 62 air cleaning specifications for filters installed upstream of cooling coils. Air Flow Measured at 500 FPM Low initial resistance for energy savings, Quality Engineered, Consistently Produced, Made of 100% synthetic Fibers, Made in the USA Two-Piece Frame Construction - will not rack, warp, or bend under normal handling or operating condition Pleats hold together even when wet! No delaminating, no excessive buckling, no collapsing ACTUAL SIZE: 17-3/8" Width X 21-1/2" Height X 3/4" Thick, Nominal Size 18" Width X 22" Height X 1" Thick