HPI Wheely King is an entry level 1:12 scale RC monster truck. Its steering servo mechanism contains a sacrificial split ring coupling called a "servo saver". When you hit a tree with your front wheel the coupling breaks and you get to buy a $11 set of parts (85260) to replace just that one small plastic piece. After going through 2 of those, I measured and printed the next one. Then a couple more. A coupler out of PLA seems to work fine. It holds up during normal use and breaks on impact, just like the original part.