Diabolos come in a number of variations: mini, small, middle, large and giant, from plastic (EVA or Hirex) or rubber, one or multi coloured depending on taste. Two tips for selling them: a larger diabolo is heavier and therefore due to its inertia is easier to play with, however for smaller children the large diabolos are not so easy to handle. The ideal size for a beginner is the middle sized diabolo. As far as the material goes, the rubber diabolos are more resistant to deformation when carried around in a bag, EVA and Hirex have stronger colours though. Playing is improves the concentration, endurance, coordination and left/right differentiation.