EXCLUSIVE! R2D2 Ultrasonic Cool Mist Humidifier Adds Moisture to Any Room and May Help Soothe Cough and Sinus congestion. There is No Filter Required and it features Anti-Microbial Protection. The unit is Whisper Silent with Adjustable Mist Output and an Auto Off Function. It has a 1 gallon capacity and lasts up to 24 hours.