ELEGANT ROOM HUMIDIFIERS naturally re­store moisture to dry interiors! Just fill the black glazed ceramic bowl with water and place the decorative white ball on top. It's made of porous clay that absorbs the water and releases just the right amount of moisture into the air through natural evaporation. No electricity needed. Greatly improves indoor air quality, especially during long, dry winter months. Set of 2 includes one large (4-1/2" diam.) and one small (3-1/2" diam.).