About The Aprilaire 4277 Humidifier Water Distribution Tray For Aprilaire 560 Series HumidifiersThe Aprilaire 4277 Humidifier Water Distribution Tray is a replacement part for Aprilaire humidifier models 560, 560A amp; 568. The Aprilaire 4277 Humidifier Water Distribution Tray distributes water across all parts of the evaporate panel evenly by attaching to the Ushaped scale control insert and incorporating a pumice coating inside.