Description
Actual Size: 20.75 x 20.75 x 4.38. Accumulair brand: 21x21x4.5 Ruud Protech 540018 compatible whole house air filters, specifically built to replace OEM Ruud Protech 540018 air filters. Fully built - no forming or combs needed. MERV graded to ASHRAE 52.2 test standards ensuring function equal to the name brand Ruud Protech 540018 filter. Photo: Example air filter image displayed is not to scale and is shown for design purposes. Brand names and Ruud Protech 540018 P/N are listed for air filter style identification use.