This is a Sponge Holder for the AnyCubic Kossel Mini that I designed in Fusion 360.
It catches dust particles off of the filament while it passes through the sponge. There are 2 small roofs that prevent the sponge from being lifted up toward the extrusion system.
I printed the sponge holder with sparse supports (10% support density), they come off easily, and any jagged leftovers actually help to keep the sponge cube in place.
To attach, use 2 of the shorter small black screws and 2 of the small silver rectangular nuts.
To use, cut a Sponge Cube that fits snugly inside the holder.
Then, take it out of the holder and pierce its center with a piece of any old filament you have laying around. I suggest to increase the hole by just a little bit, by moving the filament in a circular motion.