This duct allows to mount a 30x30mm axial fan
to the E3D extruder v5
in order to cool the core of the extruder and prevent the heat from rising up to the clamping part.
Without cooling, the filament is likely to get stuck inside the extruder, because with rising temperatures the material turns viscid outside the heater block. Therefore the extruder has to increase the effort to inject the filament.
To fix the fan to the support you will need 4 x 12mm Velox bolts