Honeywell brand air filters for Honeywell brand cabinets. We recommend always using the correct air filter for your application. Honeywell filters are 4-3/8" thick and many other brands are thicker and will not work in this application. Most sizes are listed as a nominal size. The actual sizes will vary and using an incorrect filter will allow the airflow to bypass the air filter and enter the living without being filtered which defeats the purpose of installing a high efficiency cabinet.