Polydron Magnetic Wheels Add-On Set - Engineering ExtensionAdd dynamic movement to your Magnetic Polydron constructions with this Wheels Add On Set, featuring four freely rotating wheels and hubs designed to complement any Magnetic Polydron set (except Mega Mag). These easy to use wheels introduce cause and effect concepts and basic physics through interactive play, enabling children to create moving models and explore the relationship between structure and motion. Each magnetic hub features a coloured and a