A slinky is a metal super spring that can perform a few tricks that will keep your students wondering! A slinky can travel down a flight of steps end-over-end by stretching and reforming again. A combination of gravity and momentum keep the slinky going! When you let the slinky move from one hand to the other, it will move in a fascinating motion. Slinky has been a popular toy for decades, and for good reasons! It keeps you mesmerised for hours. The super spring measures 6cm in diameter and made of metal.