This slinky is metal has a 75mm diameter and 60mm closed length.  This toy is regularly used to demonstrate waves in physics experiments as well as other useful properties.

In addition to being a terrific toy, the Slinky is an excellent device for demonstrating various properties of physics. Understanding how such properties work is essential to engineers who must apply the theories and principles of science and mathematics every day in solving practical technical problems such as harnessing the power of fuels that drive our cars, airplanes, trains, and ships; transforming water power into electricity; using steel and concrete to build dams, roads and bridges; etc.

The Slinky, like all objects, tends to resist change in its motion. Because of this inertia, if placed at the top of stairs it stays at rest without moving at all. At this point it has potential or stored energy. But once it starts down the stairs and gravity affects it, the potential energy is converted to the energy of motion, or kinetic energy, and the Slinky gracefully tumbles coil by coil down the stairs.

For simple slinky activities and the source visit Slinky® Science