For use on grass and gravel. Might not work so well on asphalt. The bigger diameter (~90mm) is useful in taller grass. If you prefer the underside of the printed part to be on the outside/inside (maybe because you use a textured printbed), feel free to mirror the TPU.stl. I tested the first print and it worked right from the printbed. The hexagonal hole is a tight fit depending on your printer tuning.
Front wheel is slimmer (25mm) vs the wheels on the back (30mm). Just for the looking :D
I used the following settings:
PLA (or PETG): 3 perimeter, 15% infill, 4 top and bottom layers, temp as needed, support!
TPU: 2 perimeter, 0% infill, 5 top and 4 bottom layers, temp as needed, NO support ;)
The two parts fit together tight and you should be able to use them without glue. However, it might be best to glue them together anyway.
The author hasn't provided the model origin yet.