Aprilaire - This replacement water panel evaporator fits models 110, 220, 500, 500A, 500M, 550, 550A, and 558 Whole-House Humidifiers. Water panel evaporators are the heart of your humidifier, designed specifically to deliver the proper humidity necessary to keep you comfortable throughout the heating season.

• Water panel slides into the scale control insert, and the water distribution tray sits across the top of the panel
• Water panel measures 9-3/4" x 10" x 1-3/4"
• Replace annually
• Designed to last the entire heating season