This is my version for the extruder filament driver for my QU-DB extruder (1.75mm filament), where I wanted to have more force applied to the filament. I guess this set will also work on MK7 extruder too, but may be there is room problems. I have added an extra 8mm spring to apply more force to the filament. Also I have change the bearing to hold a 624 bearing. Parts that you will need: - These two STL prints - x2 Spring 8mm diameter. - x1 M3 screw to hold the bearing I used the original qu-db drive gear but I wasn't very happy with it, so finally I changed to the MK7 drive gear which gave me better grip and results. Also with the MK7 i could decrease the stepper current so the motor runs cooler now ;) This design is a remix of http://www.thingiverse.com/thing:15718