Replacement filter specifically designed to replace OEM 21x26x5 Trane Perfect Fit BAYFTAH26M air filter. Rated to indpendent ANSI/ASHRAE 52.2 Test Standards which ensures filters will perform as good or better than original OEM filters. Pleated filters capture more dust than panel fiberglass filters creating a healthier environment. Thermally-bonded 100% synthetic media - no chemicals. Nominal size is 21x26x5. Acutal size is 21x26x5.