With the purchase of the new MK4, there is the addition of a piece for the filament support (filament-guide-R2) to keep the alignment of the filament without it coming out of the spool during the movement of the tool head. This part comes with 2 small plastic tubes which allow the filament to slide. But, when we printed this new part ourselves it is difficult to find this same tube. Here is my version of the printed nylon tube (I used: Talman3D - Super hard Alloy 910).