There is an improved remix of this at http://www.thingiverse.com/thing:1919259
which works better! Go use that instead :)
This is a sleeve/guide to prevent buckling of flexible filaments, and goes in the small gap between the extruder assembly and the start of the bowden tube.
In your slicer, turn it around by 180 degrees. There is a cutout cylinder at the bottom to match the bowden tube's input hole, and flipping it over will prevent any overhangs.
May have to file the inner hole a bit to get the filament smoothly travelling through it.
Openscad (source file attached)