These plastic wheels are great for makers, hobby engineers, and anyone who wants to build small car projects. Ideal for science and engineering projects, and just for fun! Quickly assemble a fast-spinning set of wheels by inserting an 1/8" dowel into the wheel, slipping a regular drinking straw over the dowel, and fitting a second wheel on the other end of the dowel. The whole wheel is about 1.4" in diameter. Please note that this product contains ONLY the plastic wheels. Other materials shown in the photos are for contextual purposes only, and are not included.