What is this crank part called? I recently had a Shun SS-8001 crankset fail. When taking it apart, I saw that the right pedal has a sort of stop ring that prevents the pedal, presumably, from unscrewing itself:



Now I need to find a replacement and I have no idea what this part is called. The pedal itself has a 35mm thread; this part seems to have a thread but also a tightening bolt. What keyword should I be searching for?
It's a bottom bracket bearings preload collar/adjuster. Just like other bearing pairs (i.e. hubs, suspension pivots, headset), bottom bracket bearings need a way to remove slack, so spindle won't move sideways. There's a thread on the inner surface, so when you turn the collar, it will move left/right along the spindle. The bolt fixes the collar in place.

If you are looking for a replacement, I'd measure the axle diameter and collar thickness. If it's 30mm/5mm, I'd try a Race Face one, or contact any Shun vendor and ask about separately sold spare parts.

Some crankarm/BB systems don't use this exact method, and some do. For example, Race Face cinch crankarms have almost the same looking collar:


SRAM has a similar tool as a part of their BB30 and now DUB crankarms:


Sometimes there's not enough space for a collar, so other options to preload bearings are:


Optional stack of flat shims on spindle and a wavy washer, here's a screenshot of Zipp Vumaquad manual, figure 3 shows a wave spring:

Shimano's Hollowtech 2 crankarms use the non-driveside arm bolt to preload the bearings: