This model is used with squash ball feet mod and MMU3 upgrade. It connects the buffer to the frame of the printer.
Here is the squash ball feet mod that I have used: https://www.printables.com/model/129548-prusa-i3-mk3-mk4-squash-ball-feet-system
I have used the longer pin. Some may find the shorter one as a better fit, that is why there are two in the files.
To use it, simply push it on the existing pin and then straight into the frame of the printer.
Organic supports are recommended.
The author marked this model as their own original creation.