Tier1 Replacement for American Standard 21x23.5x5 Merv 13 BAYFTAH23M Air Filter 2 Pack Upgraded media rated at MERV 13 to capture 90% of particles, 1 microns or smaller in size Replacement for: American Standard BAYFTAH23M and FLR06073 Up to twenty times more effective than ordinary fiberglass filters. This product is listed and rated by Underwriters Laboratories as U.L. Class 2