The all-in-one Hard Water Maintenance Kit for the April Aire 720 Humidifier includes the L Hydro Core water panel cartridge and replacement Orifice everything you need for fast, easy maintenance for hard water installations. The L Hydro Core snaps in and out, and the Orifice easily screws in and out so you ft.re done in no time. Emphasizing superior sustainability, the L Hydro Core frame is recyclable and made with recycled plastic. To maintain optimal performance and extend the lifespan of your April Aire 720 Humidifier, replace the L Hydro Core and Orifice annually for hard water applications. Changing the Orifice annually helps prevent excessive scale buildup due to hard water and helps ensure proper water supply to the L Hydro Core. If your 720 Humidifier has a hard water supply, this maintenance kit gives you peace of mind to ensure the humidifier continues to operate at peak performance year after year. Made in the USA by April Aire, a trusted leader in Indoor Air Quality solutions since 1954, the L Hydro Core water panel cartridge is a reliable and eco-friendly choice for helping to ensure a healthy and comfortable living environment. Color: Blacks.