Feel free to use it in your own designs if you need something like this. For flasks, piggy-banks or anything else. I used it myself for a base for a desklamp and it works great.(https://www.thingiverse.com/thing:3383610). See for other examples the Remixe-page of this thing.
The screw thread is rather coarse, but therefore easy printable and well scalable. The mitered top of the plug and opening ensure that it can be tightened securely.
Happy designing :)
3-Nov-2019) Added a STP-file of the thing
Fillopening_with_plug1.stl | 413.4KB | |
Fillopening_with_plug1.stp | 2.7MB |