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You will require;
Smooth ball spring plungers (5mm diameter, 6mm High)x2.
They can be purchased from BamuLab's shop under the maker's supply section for a few dollars, part#FB004. I think they come in a pack of ten. The two ball plungers are inserted into the holes on the hex protrusion of Box B.

No supports are required.
Toilet roll dispenser version can be found here:

https://www.printables.com/model/1611459-tissue-box-dispenser-for-toilet-rolls
Happy printing.
The author marked this model as their own original creation.