Replacement HAC-504 filter for Honeywell - Compatible with Honeywell HCM-300T, Honeywell HCM-350, HCM-631, HAC-504AW, HCM-710, HCM-315T, HAC-504, HCM-630, HCM-300, Enviracaire ECM-250i Replacement HAC-504 filter for Honeywell - Compatible with Honeywell HCM-300T, Honeywell HCM-350, Honeywell HCM-631, Honeywell HAC-504AW, Honeywell HCM-710, Honeywell HCM-315T, Honeywell HAC-504, Honeywell HCM-630, Honeywell HCM-300, Enviracaire ECM-250i, Honeywell HCM-600, Honeywell HCM-500, Honeywell HCM-2020, Honeywell HCM-2000, Honeywell HCM-1000, Honeywell HCM2000, Honeywell HCM1000, Relion RH1300, Honeywell HCM-650, Honeywell HCM-646, Honeywell HCM-645, Honeywell HCM-640BW Replaces Honeywell HAC504 Humidifier filter Traps Water Impurities & Dissolved Solids Before They Become Airborne For best results, change air filter at least once per season or more often depending on air quality and use. Essential for Allergy Sufferers. On Sale for a Limited Time!