Use this versatile looping track to demonstrate topics including acceleration, critical velocity, centripetal force, and Conservation of Energy. Size and price perfect for use by students in classroom laboratories. One 3/4" steel ball and one 5/8" steel ball included. 3/4" wooden and glass balls available separately. Dimensions: Base: 16", Loop diameter: 8", Overall Height: 20". Available in sets of 8 only. Shipped directly from manufacturer.