21x23.5x5 (20.1x23.2x5) MERV 11 Trane Aftermarket Replacement Filter Trane Perfect Fit air filter #BAYFTAH23M, TFM235A0AH00, TFM235A0AH10, TFM235B0AH01, and TFM235B0AH0A Nominal size 21" x 23 Actual Size 20.1" x 23.2" x 5" 98% efficient filtration media This is an aftermarket filter.