This is a replacement cap for a umbrella as those get lost easily and i couldn't find one online.
The thread is non-standard, so it's modelled with a afair amount of trial and error, but works quite well and can be screwed into the top of the umbrella very tightly.

Print with high infill to have some infill inside the thread (the cap itself will be mostly massive).
No supports required.

Creality

Ender 3

No

No

0.16

40%