Summary

The hole for keyring is ~2.5–3mm wide. I recommend using a smaller ring on it and attaching a bigger one after that one.

This thing was made with Inkscape and Tinkercad.
You can edit the outlined version here: https://www.tinkercad.com/things/ctObmfkZmlX
The filled version can be found here: https://tinkercad.com/things/4quej0JBePy

Print Settings

Printer:

Wanhao Duplicator 4S

                                            <p class="detail-setting rafts"><strong>Rafts: </strong>                     <div><p>No</p></div></p>                                                                                <p class="detail-setting supports"><strong>Supports: </strong>                     <div><p>No</p></div></p>                                                                                <p class="detail-setting resolution"><strong>Resolution: </strong>                     <div><p>0.3mm</p></div></p>                                                                                <p class="detail-setting infill"><strong>Infill: </strong>                     <div><p>100%</p></div></p>

VW Beetle Keychain