Spring Loaded Extruder Upgrade Mbot

It is a simple filament drive replacement for printers whose original filament drive has smaller dimensions than Makerbot's. I looked at the http://www.thingiverse.com/thing:42250 and http://www.thingiverse.com/thing:94979 and found they are much bigger than I need - 42x29x15,2mm for Mbot3D Cube. So I've designed my own filament drive guide based on the respectful works mentioned above. SW2012 sources included.

Also you'll need:
1) M4x10 countersum screw
2) M3x8 countersum screw
3) bear