There are four models. The first one is a print in place model. For the others, you have to first print a ring (rounded or not); then, to print the stick, you will have to modify the .gcode (ex. in cura) to make a pause at 30mm height to put the ring in it. If you slice it in cura don't forget to activate "redo layer". There is no working difference between the rounded ring and the normal one. So print them and have fun !!!
I'd be happy to see some makes ;)
The author hasn't provided the model origin yet.