Actual dimensions are 19.13 x 19.88 x 4.25. Accumulair brand 19x20x4.25 Day and Night FILBBFNC0021 style whole house air filters, specifically engineered to be an alternative to the original brand Day and Night FILBBFNC0021 filters. Completely box-formed with no assembly or combs needed. MERV graded to ASHRAE 52.2 test standards establishing performance equal to the name brand Day and Night FILBBFNC0021 air filters. Note: The sample air filter pic displayed is not the actual dimensions and is included to show construction purposes only. Trade names and Day and Night FILBBFNC0021 P/N are listed for air filter substitution identification purposes only.