The Aprilaire 600 Humidifier Water Panel Evaporator is a Compatible metal humidifier filter. This filter draws dry air through the wet humidifier filter. The dry air that passes through the wet Aprilaire humidifier filter picks up moisture, thereby humidifying the air in the house.
The Aprilaire 35 water panel evaporator has a filter life of about 6 months - the dimensions of this Aprilaire humidifier evaporator filter are approximately 10" x 13" x 1 3/4". This is the Aprilaire "compatible" filter.