Lennox Healthy Climate #35 Water Panel Evaporator- # X2661, 2-Pack The "heart" of your whole-house humidifier, the Water Panel (also known as humidifier filter, water pad, evaporator pad), should be changed at least once per heating season. The pad is constructed of an expanded aluminum honeycomb mesh that is dipped in a clay coating. This coating is able to absorb and hold water. Warm, dry air is forced through the wet pad to introduce water vapor into the home. Product Features: Factory original OEM part Honeycomb filtration to trap mineral pollutants found in water and help prevent them from entering your home. For optimum performance, replace panel once every 6 months or more often in hard water areas. Specifications: Size: 10 x 13 x 1-1/2 Fits the Following Humidifiers: Healthy Climate: HCWB3-17 HCWB3-17A HCWP3-18 HCWP3-18A HCWB2-17 HCWB2-17A HCWP2-18 HCWP2-18A WB2-17 WB2-17A WP2-18 WP2-18A Aprilaire: 350 360 560 560A 568 600 700 760 760A 768 Click here for instructions on changing out your water panel