Marble runs come in many various forms, but essentially consist of a marble running along rails or track. They can be made from wood (most of ours are), or from plastic, or indeed anything that will allow a marble to roll down freely. Marble runs can also be used with cars instead of marbles.
Most marble run structures offer some form of flexibility in terms of builds. Depending on the set, your kid can add as many twists and turns to the marble run track as they want. From simple to a more complex marble run tracks, we've got them here at Fluff Heaven.