DERBY WORX PRO ULTRA LITES have won derby races at every level from coast to coast and continue to be the number one choice of both top racers and repeat district champs everywhere. These wheels are precision machined on a $30,000 CNC lathe. The wheel diameter (radial runout) is controlled to within an amazing 0.0005 inches. The OD of the wheel is lightly machined. This makes the OD of the wheel concentric to the wheel bore and removes any imperfections on the wheel for a perfectly flat and concentric wheel. The axle hubs have  been reamed ever so lightly to straighten the hub and help with your alignment then they are burnished to smooth finish.  The outer friction robbing step has been removed and replaced with a cone as well as the inner hub is lightly trued and coned to provide the ULTIMATE in performance! The inside of the wheel is machined to remove material thus creating the ultra light wheel without modifying the outward appearance of the wheel.. Lighter wheels have less rotational mass, they start quicker and turn much easier than standard BSA® pine wood derby wheels. Lighter wheels also allow you to put more weight to rear of car which gives your car more potential energy to release as the car rolls down the track. Wheels are matched by mold number for a perfectly matched set of wheels. All material is removed from inside the wheel and the wheels are Stock Appearing from the outside from the full width tread to the radiused inside edge.