Prusa Mendel Filament guide
by jpaandu, published
This piece clamps onto the two parallel threaded rods between the Z motors on a prusa or mendel reprap 3d printer. Pass the filament through the hole on the top and into the extruder. Can be used with dual extruders as well, only need to enlarge the top hole a bit if you're using 3mm filament.
The elliptical bell-like structure allows for free movement of the extruder along the X-axis without stressing the filament too much.