Designed to Fit Honeywell HCM-600, HCM-710, HCM-300T, HCM315T, HCM-1000 series, HCM-2000 series, HCM-300 series, HCM-600 series, HCM-700 series, ECM-250i. For use with cool moisture evaporative humidifiers. Package contains 1 filter. OEM #HAC-504AW