The modern 'Circular Motion Kit' is a new way to perform experiments in the classroom so that the results are accurate. The old PSSC style 'Circular Motion' or 'Centripetal Force' system was performed outdoors where weights in the form of washers are spun in a big circle around a student's head. It has never provided good results. In addition it is quite dangerous (see MF0850-001).
This system is compact, much safer, is fun to do and results are very convincing.
see the PDF file for more detail and the correct technique.