Build four brilliant balloon-powered racers in Air Power. Children can have rocket-propelled fun with these easy-to-assemble creations, including a hovercraft and an original Klutz balloon-powered rocket! The book comes with every part needed to make the racers work; including five balloons, straws, wheels, axles, two mouths pieces and stickers! Everything is explained with clear building instructions and understandable scientific explanations. Perfect for budding engineers!.