I travel a lot with my SCX6 in the trunk; it moved around a lot on its tray. Adding these kept it in place.
You'll need to print two per wheel; you'll also need some ¼in rope/para-cord to connect them. I found it best to put the chocks around the wheels and then cut the rope so you can make knots and cut to length accordingly; you want a pretty tight fit.
You're looking at about 5hr 45min on a MK2.5S and 2hr 20min on a X1C. I'd recommend 20% in-fill and 3 walls as these will need to be pretty tough. I've found PLA thus far is though up to the task.
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