20x25x5 (19.88x24.88x4.38) Carbon Odor Block Aftermarket Lennox Replacement Filter (2 Pack) Lennox part number X0586 Fits Lennox model number BMAC-20C Nominal size 20 x 25 x 5. Actual size (H) 19 7/8 x (W) 24 7/8 x (D) 4 3/8. This is an aftermarket filter.