I bought this toy for use in a summer hands-on traveling science museum.  It has proved to be very durable and was well worth my investment.  I purchased two sets for the exhibit, which allowed more than one child to play at one time.  Besides being well-made, the designer put thought into the extra gizmos so that the junior engineers could find a wide variety of ways to distribute the motion of the gears.  There was one little tiny part that we couldn't figure out the function for, but that did not detract at all from the overall use of the product.