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, you’re 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 humidifier’s cartridge provides up to 30-40 full tank uses depending on your water’s hardness WHAT’S IN THE BOX - (1) Pack of 4 Homedics Ultrasonic Humidifier Demineralization Cartridges