This 13cm diameter molded wheel contains four grooves of different diameters in the ratios 1, 3, 5 and 7. The grooves are wide and flat-bottomed insuring an exact diameter for each groove; each comes with a small hole to retain the cord. The back of the wheel is hollow to minimize its mass and inertia. The entire unit is attached to a 14 x 1.3cm rod.
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