These are basic thread boards holders, of various sizes, suitable for Duncan Rhodes Paint Academy paints. These paint bottles are 24mm in diameter, so anything around there would fit. I've also made a similar set for the Citadel range of paint bottles (which are 33mm in diameter), as well as a set for spray paint. All for mounting on the Threadboards (kickstarter).
For the Citadel version, see this page.
Some of these models will require a larger printer, such as the Prusa XL, but most of them should print fine on the MK3 and MK4. You may have to rotate the model 45 degrees, to allow them to fit on your plates.
The holders comes in two main models:
I personally don't really like the Double Row, because I like to see the full label of each paint. However, they are still useful, particularly for storing larger amounts of paint bottles.
The sizes varies based on the number of paints each model holds. The names are the width and the length of the model, as well the number of paint bottles it holds.
The author marked this model as their own original creation.