HQRP Filter for Holmes Humidifier HM3655, HM3655BF, HM3656BF, HM3656 Coaster HQRP&reg; Humidifier Wick Filter Replacement + HQRP&reg; Coaster; Improves efficiency of the humidifier, traps mineral deposits from the water; Extended filter life with help of reinforced layer; Replace filter every 4-6 weeks, depending on usage and hardness of water; 2 weeks DOA replacement warranty!