Extra large, unbreakable, clear plastic housing makes this functioning lung model the best available. The functioning lungs can be seen from the back of the classroom as you demonstrate the principle of differential air pressure. The use of rubber stoppers on the ends of the bronchus makes replacing worn out lungs much easier than traditional models using string or rubber bands. The handle on the durable, latex diaphragm allows for easier expansion of the balloon lungs during operation. A real must for your human anatomy unit. Measures 5¾" x 11", comes assembled with BioFax! instructions.