16x26x5 (16.38x25.5x4.38) MERV 13 Aftermarket Lennox Replacement Filter (2 Pack) Nominal size 16" x 26" x 5". Actual size 16 3/8" x 25 1/2" x 4 3/8". Pre-applied gasketing on the assembled filter prevents air by-pass. 98% efficient filtration media. This is an aftermarket filter.