I originally designed this for the https://www.printables.com/model/495173-flat-pocket-whistle by Jonas Daehnert, and I recommend using it for that.
This clip does not fully close, and that might be impossible because of tolerance limitations, so it has a chance of slipping out when attached to a hole in a thin material.
If you want a complete seal, then you can add a drop of hot glue to the gap.