Keep your Aprilaire humidifier running at peak efficiency with the Aprilaire 4788 Maintenance Kit. Designed specifically for the Aprilaire 400 Series—models 400, 400A, 400M, and more—this all-in-one kit provides everything you need for annual maintenance. From replacing the water panel to refreshing internal components, the 4788 kit helps restore optimal humidity control to your home. All components are made in the USA, ensuring quality and performance you can rely on.