Domino Rally

Different sets were produced, each consisting of several hundred multicolored plastic dominoes. They were not solid rectangular prisms, but rather were hollowed out on one side. The injection molding process used to make them also tended to leave protrusions on the standing edge. As such, they tended to fall over easily, particularly when being set up on the stepped staircases and bridges that came with the set. Newer dominoes were made which left the plastic in the middle, resulting in the dominoes standing upright much better than before.^{[citation needed]}