Lets the flow ring flow up and down your arms by simply raising and dropping your outstretched arm. Works better on bare arms/on tight and smooth sleeves. It gives an incredible sensation on the arm and can be a great visual stim because the rings spin around quickly as it moves, which gives a colourful, blurred, spiral effect.
If you would like to figure out how it works, here's a YouTube video as an example: https://www.youtube.com/watch?v=2xzY-uKGNM4
 
Fidget tools can be great in assisting and encouraging:
Stress and emotional management
Self-regulation
Focus and concentration
Tactile awareness
Strengthening of hands