Here's a paradox-a device that remains balanced when a heavy plastic tube dangles from one end while being supported at the opposite end by a single fingertip. Remove the tube and the device falls. How can this be? It's center of gravity! This simple device will be a real show-stopper as you introduce your students to the concept of center of gravity. Kit includes demonstration instructions, plastic tubing and durable plastic balancing device. All the materials are completely reusable.