The HoMedics UHE-HDC4C Ultrasonic Demineralization Humidifier Replacement Cartridges are designed for tabletop use and feature ultrasonic humidification technology. These cartridges, in a sleek blue color, are made of plastic and are designed to fit the HoMedics UHE-HDC4 model. Perfect for improving indoor air quality and providing a clean and healthy environment, these cartridges offer a hassle-free solution for maintaining optimal humidity levels in your home.