HQRP Filter 6-pack for Bionaire BCM4600 BCM4655 BCM4655-CN BCM5520 BCM5520RC BCM5521 Humidifier + HQRP Coaster HQRP&reg; 6-pack Cool Mist Humidifier Filter Replacement plus HQRP&reg; Coaster; Filter Helps To Capture Mineral Deposits And Improve Efficiency Of The Humidifier; For Maximum Performance Change Filter Every 30 Days; 100% Compatible with Original filter. 2 weeks DOA replacement warranty!