The IEC 'Wave Demonstration Spring Set' is a pair of special springs used for teaching wave motion. The large spring (75x110mm DxL) is known as the 'Lazy Dazy' or 'Slinky' spring and it stretches out to about 10m long. It is used for demonstration of transverse wave motion, standing waves and so on. The other spring is a long thin spring (20x1800mm DxL) which can be stretched to about 10m long. This is used for demonstrations of longitudinal wave motion and standing waves. We also supply these springs individually.