Replacement for Parts # WF813, AC813, PCWF813, PCWF813-24, RWF-813. Compatible with ProCare PCCM-832N, PCCM-840 Cool Mist Humidifier. HQRP Humidifier Filter features Honeycomb filtration to trap mineral pollutants found in water. For optimum performance, replace filter at the beginning of each season or every 2 months depending on use.