This is a simple derailleur cable redirector. Some derailleurs (most notably, the Shimano GRX series) will redirect the end of the cable directly into the wheel requiring you to cut the end of the cable, even if by a measly few millimeters, to avoid hitting the spokes. Dumb cable routing aside, it's one of the better derailleurs I've had as far as reliability and time between adjustments. That said, it's not the only derailleur I've ever used that made it difficult to manage the uncut cable.

I created this clip primarily to allow you to direct the slack away from the wheel, without cutting the cable and having to worry about premature fraying, strands pulling out of the cap, and so on.

Printing

Due to the small size, I would recommend applying a thin layer of 3D printing glue to your print surface, then printing at whatever settings you want. I tested it at both 0.08 mm and 0.20 mm without issue. This is not a load bearing part, so you don't have to worry too much about infill or walls. The defaults of your slicer will most likely be more than sufficient.

Assembly

For assembly, I recommend curling the cable into the groove first. It was made deep enough, and provides enough friction, that you don't have to worry too much about the cable slipping out if you have to stand up to get the cap.

The hole in the cap, and in the actual redirector body are both measured for an M3 bolt. You can also use an appropriate cable tie if you'd like.

When ready, place the cap on, tighten down the bolt or wire tie, then slide the redirector around as appropriate if you want to make small adjustments to how it curls the end.