Aprilaire - This replacement water panel evaporator fits models 400, 400A, and 400M. 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 10" x 12-3/4" x 1-3/4"
• Replace water panel twice per season