This wheel is the official 3D printed wheel for the X-Derby. Feel free to download and print for the Official race. We recommend PLA, but ABS works too. .3 mm Z 100% fill What is the X-Derby? Think Boy Scout Pinewood Derby with minimal rules. The track is larger and undulating. Few restrictions on size or materials that you can use to build your car. Prizes for fastest car and most creative plus many more. Have fun, being creative and innovative in materials and designs and learn some engineering techniques along the way. Don't have a 3D printer? Get it printed locally here; http://www.3dhubs.com/bend/hubs/hdmmThe model was created in Autodesk Fusion360. The hub was designed to use 16 gauge nails 1.25" long as axles. There is also a guide that can be printed to help make holes for the nails. To drill the holes cut the head off of a 16 gauge nail and chuck it up in an electric drill. Make sure that you do not drill the full 1.25" depth so the axle nail will seat firmly. For more information please visit http://www.makermill.org