Fantastic for teaching the properties of air, Bernoulli's Principle, and NOW for building structures! Windtubes are like balloons that don't stretch. They are not elastic. About 8 feet long and 10 inches in diameter, they are huge! It takes as many as 70 breaths of air to fill a Windtube or as few as one breath if you use Bernoulli's Principle. It is amazing to watch -- even some magicians use them in their act. The illustrated instructions include over a dozen creative and educational activities that you can do with Windtubes. The inventor Doron Gazit suggests connecting them together with simple rubber bands to create space frames or even Buckminster Fuller structures.