Hub for mounting the tire from a set of foam or rubber model airplane wheels to a 6mm shaft.Additional hardware required for each hub: After printing, carefully remove all the support from inside the nut slots and insert the square nuts. Once they're aligned, I recommend plugging the slots so they can't slide back out; I used hot glue for this. Slide the hub on the shaft and then insert and tighten the set screw. To remove the model airplane tire from the hub it comes with, you can slide a couple thin pieces of metal between the hub and tire and work it off like using tire levers on a bicycle tire. Once you have the tire, slide it on the mounted hub and position the outer plate and machine screws. You made need to squeeze the tire between the hub and the plate before you can get the threads on the screw mating with the nut. After assembly, make sure that the wheel is true; if the wheel needs truing simply tighten or loosen the nearest machine screw. For my outer plates, I cut some polycarbonate with a hole saw and then drilled holes for the machine screws to pass through. If requested, I can make a simple outer plate STL to be printed.