HoMedics Demineralization Cartridge for Ultrasonic Humidifiers 4-Pack Humidifier Filter Replacements, Filters Mineral Deposits and Purifies Water in Air Humidifiers for Bedroom, Plants, Office Blue - DEMINERALIZATION CARTRIDGE The Homedics Demineralization Cartridge humidifier filters help reduce the potential for mineral residue (white dust) containing calcium, lime, and magnesium caused by minerals and chemicals in hard water - SIMPLE INSTALLATION - Once inserted into your Homedics humidifier tank, youre ready for use; pack of 4 for months of use and easy replacement - ULTRASONIC HUMIDIFIER COMPATIBLE The Homedics filter replacement works with any personal Homedics ultrasonic humidifier with a 0.5-gallon tank or larger - REPLACEMENT CARTRIDGES - Each cool mist humidifiers cartridge provides up to 30-40 full tank uses depending on your waters hardness - WHATS IN THE BOX - (1) Pack of 4 Homedics Ultrasonic Humidifier Demineralization Cartridges