One of my favourite keyrings ever has been this aluminum ring I extracted from a harddrive I took apart when I was a child. It's sturdy, light weight and lets me hang my keys in any hook.

This project is a tribute to that little ring made to exact same dimensions. 30.2mm outer diameter, 25mm inner diameter with a height of 5.6mm and champfer of 0.3mm. The printed ring is still plenty strong and I cannot crush it with my bare hand(your results may vary).

I use the original one on my bike key and I added the new one to my home keys. I included the Freecad model so you can modify it to your heart's content.

TL;DR: It's a plastic ring with a small chamfer. That's it. I hope you like it.