The metal Slinky is a coil spring that can do amazing things. We've seen many plastic versions available but they tend to not last very long, so we were very happy when we found a metal version!
You will be surprised how long you sit there watching it move back and forth between your hands. It is such a great stress reliever that you might spend the entire day playing with it.
The small one is about 4 cm tall and 2.5 cm in diameter, while the large is 7 cm tall and 6.5 cm in diameter.