The all-in-one Hard Water Maintenance Kit for the AprilAire 620 and 720 Humidifiers includes the HydroCore Water Panel Cartridge and replacement Orifice—everything you need for fast, easy maintenance. The HydroCore snaps in and out, and the Orifice is easily accessible with a thread out design so you're done in no time. To maintain optimal performance and extend the lifespan of your AprilAire 620 or 720 Humidifier, replace the HydroCore and Orifice annually if there's buildup for hard water applications or as needed. Changing the Orifice annually helps prevent excessive scale buildup due to hard water and helps ensure proper water supply to the HydroCore. If your 620 or 720 Humidifier has a hard water supply or scale buildup, this maintenance kit gives you peace of mind to ensure the humidifier continues to operate at peak performance year after year. Emphasizing superior sustainability, the HydroCore frame is recyclable and made with recycled plastic. Made in the USA by AprilAire, a trusted leader in Indoor Air Quality solutions since 1954, the HydroCore Water Panel Cartridge is a reliable and eco-friendly choice for helping to ensure a healthy and comfortable living environment.