This model is a straightforward, modular design meant to store multiple 1 kg filament spools mounted on a wall and to specifically fit the user's need depending on how many spools they need to store at a given time, forming a cascading pattern similar to Pascal's Triangle.
I would recommend bolting in the first (top) three (2 may work as well) for stability but the rest can hang freely, especially if there is a weight at the bottom. With these conditions, taking spools on and off shouldn't pull the lower holders out but one could easily glue them together to fix this if it does happen.
I printed them in PLA which was structurally sound enough when the weight of the spools is balanced.
Standard print settings are fine and no supports are needed.
The cylinder for the spool has a diameter of 4.7 cm and a length of 7.3 cm.
I also plan to publish an iteration that better locks the individual spool holders together with a latch of some sort.
The author hasn't provided the model origin yet.