This  Aprilaire 4218 OEM humidifier water distribution tray for use with the Aprilaire 500 Humidifier Water Panel Evaporator (Aprilaire 10) and the Aprilaire 4217 Humidifier Scale Control Insert in the following Aprilaire 500 Series humidifiers: Aprilaire 550, Aprilaire 550A, and Aprilaire 558 Humidifier.

The Aprilaire 4218 distributes water evenly to all portions of the Aprilaire 500 water panel evaporator which ensures the efficiency, longevity, and proper functioning of your Aprilaire humidifier.

This is a genuine factory replacement Aprilaire 4218 humidifier water distribution tray.