The Stepstruder MK6 is a huge leap forward for stepper driven extrusion. We've searched high and low to find a high torque NEMA17 stepper motor that is capable of direct driving 3mm filament. Using a direct drive extruder means that there is absolutely no backlash from gears. Not only that, but this spells an end to the days of DC gearmotors that are unreliable and have short lifetimes. Stepper motors effectively last forever, and these motors will provide you with thousands of hours of 3D printing awesomeness.Full instructions at: http://wiki.makerbot.com/stepstruder-mk6 or Buy the complete kit online at: http://store.makerbot.com/stepstruder-mk6.html Or the kit to upgrade your existing MK5: http://store.makerbot.com/stepstruder-mk6-upgrade.html