The Kâ€™NEX Double Ferris Wheel is more than a building project; when finished, it is a decorative display forÂ a childâ€™s room. We think this toy has it all. The Double Ferris Wheel from K’NEX treats kids ages eight and up to the fun of building two star-shaped wheels that spin in opposite directions and stand over three feet tall. Each set includes more than 850 brightly colored pieces, new adapters and connectors, and a motor that powers the wheels. The suggested retail price is $29.99. At less than $30, this is a terrific birthday present. The set requires two AA batteries.