21x21.5x5 (20.1x21.1x5) MERV 13 Aftermarket Trane Replacement Filter (2 Pack) Trane Perfect Fit air filter #BAYFTAH21M, TFM215A0AH00, TFM215A0AH10, TFM215B0AH01, and TFM215B0AH0A Nominal size 21" x 21 Actual Size 20.1" x 21.1" x 5" 98% efficient filtration media This is an aftermarket filter.