2-pack Original Factory Replacement FC40R1128 14 x 24 x 5 (actual size 13 3/4" X 23 3/4" X 4 3/8") MERV 10Replaces older Honeywell model number F35R. The FC40R Return Grille Filter is a high-efficiency, long-life replacement for return grille applications. It captures a significant amount of the airborne particles in the air that circulate through the filter. (Honeywell recommends allowing a depth of seven inches behind the grille to provide space for the deeper filter and airflow through the filter.) Honeywell recommends changing your filter once a year. It may be necessary to replace it sooner depending on the conditions in your home.Â Filter features 1"Â lip around upstream side FEATURES Â Mounts in most third party return filter grilles (features integral gasket around upstream side of filter). Â Provides high-efficiency alternative to one-inch filter. Â Captures particles as small as 0.3 micron. Â Pleated filter for greater media capacity. Â Easy installation. Pre-assembled filter easily inserts into and out of existing return grille. Â Exclusive frame design nests properly into place. Â Low pressure drop reduces strain on equipment, provides a comfortable air flow and maintains equipment efficiency longer than standard filters.