20x20x4 (19.5x19.5x3.75) MERV 11 Aftermarket White Rodgers Replacement Filter (2 Pack) Nominal size 20" x 20" x 4". Actual Size 19 1/2" x 19 1/2" x 3 3/4". 98% efficient filtration media. High efficiency filter media collects small dust particles before they can collect on your coils. This is an aftermarket filter.