It's printed in “vase spiral mode” of red transparent PET-G at 0.2mm resolution.
Nozzle size 0.4mm at 220 degree Celsius. For the Anet A6 this object was printed on,
it was necessary to reduce the flow-rate to 80%, printing with this PET-G.
But this flow-rate setting may vary on other printers.
On other printers, experimenting with vase spiral mode,
it works even on 49% Flow-rate with PET-G.
Also printing slow with PET-G gives much better results.
That means like 25mm/sec or slower :-)
PS: I may have re-scaled the object in the slicer programs.