The Derby Worx DWXPS01 Precision Stocks (2.4 gram) are the absolute best mold matched and machined wheel you can get with every point being corrected including the axle hub! The ultra smooth tread looks virtually untouched but it is by far the most accurate on the market today. Each set of wheels is made using parts which came from the Official BSA® Grand Prix kit, hand selected into mold matching sets then professionally machined to perfection on a CNC lathe for maximum performance. 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! If you are looking for that extra bit of needed speed for your pinewood derby with a non-lightened or heavily modified wheel, these wheels are a must!