HQRP Filter 3-Pack for Holmes HM3300 HM3400 HM3500 HM3501 HM3600 HM3607 HM3608 HM3640 HM3641 HM3650 Humidifier Coaster HQRP&reg; 3-pack Cool Mist Humidifier Wick Filter "D" 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; Compatible with Original filter. 2 weeks DOA replacement warranty!