This Cleaning Brush is designed specifically for cleaning the ultrasonic transducer on the following AIR-O-SWISS Ultrasonics: AOS 7131, AOS 7133, AOS 7135, AOS 7142, AOS 7144, AOS 7145, AOS 7146. The Cleaning Brush color can be white or yellow. Be sure to order the correct parts for your model to keep your AIR-O-SWISS unit functioning properly.