17.5x27x5 (17.2x26.2x5) MERV 11 Aftermarket Trane Replacement Filter (2 Pack) Nominal size is 17 1/2 x 27 x 5. Actual size is 17.2 x 26.2 x 5. 98% efficient filtration media. Up to twenty times more effective than ordinary fiberglass filters. High efficiency filter media collects small dust particles before they can collect on your coils. This is an aftermarket filter.