Protec, Continuous Humidifier Cleaning Cartridge, Continuous Protection Against Bacteria, Mold, Fungi & Algae In Your Humidifier, Fresher, Cleaner Mist, Humidifier Stays Cleaner, Longer, Easy To Use, Simply Drop Cartridge Into The Tank, Lasts 30 To 40 Fillings, Safe, Non-Toxic & Odor Free, Works In All Humidifiers, Extends Filter Life, Humid Clean Cartridge PC-1V1, TV #521-755.