The Prusa filament guide is an optional add-on for the MK4, which comes with PTFE inserts to be used with it. That filament guide also fits the MK3, but you will need to make your own PTFE inserts.
This cutting jig takes 10mm PTFE tube (8mm internal diameter) and will make equivalents to the pre-cut MK4 inserts. Hold the knife towards the open end of the guide as you cut, this helps push the cut piece tight against the closed side and keeps the cut straight.
You will also need 3 M3 hex nuts, 2 M3x10 screws and 1 M3x18 screw, as shown in the Prusa assembly instructions.
The author marked this model as their own original creation.