This is a 3D printable mold for casting your tires.  Ninja Flex is expensive, and many extruders won't handle it, this is an alternative way of making your tires yourself.  You only need to cast one copy of the mold and you can cast all the tires you need from it. I use Oogoo for casting my tires and you can find the recipient here:

http://www.instructables.com/id/How-To-Make-Your-Own-Sugru-Substitute/ Oogoo sets in less than 10 minutes so printing molds is a great way to build up a bunch of tires fast.  Add a few drops of essential oil to the mix and after a few days your object will smell like that instead of vinegar. Have fun.