This is a custom mount for the MMU2 which holds it horizontally. It is also higher to allow for clearance of the extruder when printing tall prints.
I use this along with my angled buffer mounts to create a low resistance path from spool to extruder:
https://www.prusaprinters.org/prints/15130-mmu2s-buffer-angle-mount
Category: 3D Printer Accessories
The author marked this model as their own original creation. Imported from Thingiverse.