Replacement warm mist humidifier absorption sleeve for Optimus model 2-1/2-gallon Warm Mist Humidifier model U-32000, 3.0-gallon Warm Mist Humidifier model U-32010, 3-1/2-gallon Warm Mist Humidifier model U-32030 and Kenmore models #15123 and #15125. This filter helps to protect against bacteria more effectively as well as reduce the mineral buildup on the heating element. Filter also prevents the noisy gurgling sound to help you sleep more soundly at night. Each pack contains 3 filters.