Star 33604 Radiators Humidifier, Ceramic, Horn-shaped Pendant (Pack of 4) Practical radiators humidifier equipped with universal hook, it fits easily onto covered radiators and free-standing units Material: Ceramic - Dimensions 7 x 4.5 x 18 cm (about 2.75 x 1.77 x 7.08 inches) It improves the air quality in the room by adding humidity trough natural evaporation Just fill it with tap water and attach it to your radiator No need for filters or chemicals like antibacterial or cleaning solutions