Fischertechnik-Rolling-Action-Construction-Kit-Fischertechnik-516183-Watch-as-balls-whiz-around-the-unique-Flex Rails-by-different-routes-See-them-accelerate-brake-release-a-chain-reaction-shoot-through-loops-traverse-see-saws-or-be-lifted-up-by-a-hoist-with-a-counter-weight-triggered-by-a-release-lever-or-pre-tensioned-catapult-Fischertechnik-Rolling-Action-Construction-Kit