Experience new marble run fun. The ROKR Parallel World series blends modern cyber design with marble runs in a box. Each box features a unique design style and can be displayed on your desk, letting you watch balls race along the tracks inside, enhanced by dazzling multi-light effects. What makes it even cooler is that its expandable play boxes can be connected with lifts to form a larger system, allowing the steel balls to run endlessly across multiple worlds.
Source: https://www.robotimeonline.com/collections/rokr-parallel-world