Robocar Poli Mylar Balloons Every Robocar Poli fan will love these mylar balloons. Measures approx. 28cm (11in) in diameter. Each balloon comes with the windmill and stick. Simply inflate them by inserting a straw into the air outlet and blow manually. For more fun, fill them with helium gas. Self sealable once inflated. To reuse mylar balloons, just pump them up again whenever needed and you are good to go.