Honeywell TRN2127R1/E 5-Inch High Efficiency Air Cleaner Filter, 27-Inch by 21-Inch by 5-Inch MERV 10 Rating - Up to 20 Times More Efficient Than Typical 5-Inch Pleated Filter Fits Trane or American Standard Perfect Fit Captures High Percentage of Household Airborne Particles, Including Microscopic Particles You Can't See Consumer No Longer Has To Wait For HVAC Rep To Replace Filter; Actual Size 20.8 by 26.2 by 4.9 Lasts Up To Six Months