The Open Box AIR-O-SWISS AOS 7531 Demineralization Cartridge Unit is a beige-colored, plastic cartridge unit with a tank capacity of 7.5 L. It is designed for electrical power sources and operates at 24V. The unit features ultrasonic humidification and has a compact size suitable for various rooms such as the bedroom, bathroom, or hallway. With its focus on demineralization, this cartridge unit from the reputable AIR-O-SWISS brand is a reliable choice for improving indoor air quality in small to medium-sized spaces.