Like many Sintron Prusa I3 builders, I had to upgrade the MK8 extruder mount so it would hold the stepper firmly. I wondered if the hole in the center of the mount was intended for something, but never saw anything. This simple fan shroud clips into the center hole on the MK8 extruder motor mount and easily comes off when needed.I printed in ABS, 4 layers solid top.bottom 3 perimeter, 40% fill, 0.3 layer with 0.4 nozzle.