About this 3D model

it's designed to fit this: http://www.thingiverse.com/thing:31267 and guide the filament to the hobbed bolt, at the beginning i added that plastic tube, it's the inner tubing of a pen, the one that holds the ink, it's perfect for 1.75mm filament. but one time it moved and got jammed in the hobbed bolt so i took it out, it's not necessary.