The design concept is pretty simple and straight forward. It consists of the following piece types and quantities:
For a complete set, you will need to print all 4 pieces, have a string or a ball chain (with 3mm diameter balls) and a rubber band or traction spring.
Regarding the issue of why there are so many different models, it is due to the way they are meant to be assembled. The three types of bases are intended for three distinct “traction” piece types.
The following list explains each base type:
It's important to state, that not all models are compatible with each other. The compatible ones are listed here referring to their file names:
This is mainly due to the thickness of the compression piece, this being 3mm & 5mm for the thin & thick ones respectively.
Printed in PLA, without rafts, at 0.2mm resolution and 100% infill for the compression pieces and %15 for the bases.
The use of supports is not really required is your printed is properly calibrated. If you want to be safe, and use supports, I will suggest to put the fit hole, the one where the compression model fits, always in the up side.
The assembly of this one is a bit tricky, and for each base type is a little different, although the first part is the same: insert the compression piece and glue into the base of your choice. Just as seen on the following three .GIFs:
“Loop base” type compression piece assembly (you will need to do this twice):

“Knot base” type compression piece assembly (you will need to do this twice):

“Ball chain base” type compression piece assembly (you will need to do this twice):

As briefly mention earlier, each vase type is assembled differently:

For all the 3 cases, the traction part should measure around 13cm being basically the total high of the contraption once assembled.
Finally, once the compression part is glued and the traction part of choice is cut and put into place, you will need a central traction part. You can use a traction spring (see the annex for the one that I have used) or you can simply put a rubber band! just as seen in the following .GIF:

The dimmensions of the ball chain that I have used:

A 360º .GIF of the ball chain base type assembled:

The strigs that I used were this ones from Amazon:
The author marked this model as their own original creation.