Can a tool this small make a big difference in how your Pinewood Derby® car performs? The answer: absolutely! With tires, the differences are roundness and smoothness. And the rule is: the rounder and smoother the tire, the faster your car is going to be. Use the Wheel Truing Mandrel Set tool to achieve this. Includes: mandrel and 1 sheet each of 120- and 220-grit sandpaper. Age: 8+