This mechanical DIY wooden bus model is an exciting addition to Ugears' Harry Potter collection and a true technical masterpiece. To set the bus in motion, hold it firmly and press down on the magical manipulator button. Then release it, and the Knight Bus roars away thanks to its gear system, which transfers the energy from the spring to the wheels. The tilting gear allows the bus to continue rolling while idling. The most important feature of the Knight Bus model kit is its ability to change its mass with a twist of the magical manipulator, becoming narrower or wider. Turn the knob on the roof of the bus counterclockwise to make the bus narrower, allowing it to weave through traffic. Turn the knob clockwise to expand it (and all its passengers) back to its original size. As the width of the bus changes, so does its speed. In its normal (non-compressed) state, the bus moves incredibly fast. When you make the bus narrower, an internal mechanism allows it to travel in slow motion.