This is a fully printable feeder upgrade for the Ultimaker. It improves by far the feed of the filament by reducing a the friction generated by the stock parts.
Just print it and ad a 10x6x3 roller. Remove the stock Ultimaker part and replace it with this one :)
Edit: Uploaded a video of the piece mounted on the Ultimaker: http://youtu.be/OAo04N6xTbs