This is a Direct-drive hinged extruder for E3D/J-Head hot-end. The M4 holes have a 8mm spacing so it can fit with the Makeblock system, but you could use it on other printers too. The compact design will also allow Mendel-like printers to easily host two extruders (one resting on each side) without loosing too much X-space. This is the second version as the first was too flimsy. This one uses a MK8 pinch wheel + a 608 bearing (the standard skateboard size). Print all parts in ABS as PLA will deform over time due to stepper motor heat (often 60-80C).