My son wanted a little keychain/charm to attach to his school water bottle, and the existing ones didn't print well. I did it this way to keep them key loop laying flat on the build plate so it could stay thin (and thus easier to get on a small key ring) yet strong due to the print orientation. 

The 10mm variant (tiny and cute) prints just fine with a 0.4mm nozzle, and the 17.5 mm version is closer to what I typically see on keychains.

The two halves fit together with a pretty snug friction fit, no snap ring or anything. Just the layer lines and friction seem more than enough. There is a 0.15mm tolerance on the fit.

I used Sunlu's PETG Green (which prints great!) and I painted the black with nail polish and a toothpick.