The MaxFlo print cooling system includes a carefully sculpted manifold and gasket.  The manifold delivers air from the model cooling turbine fan to the 4 slots visable in the bottom of the Xmax and Xplus carriages.  The gasket plugs the original hole through which the factory J hook passed through.  The advantage of the MaxFlo is in that it cools evenly with downward forced air, while not blowing on the extruder nozzle like the J hook, which can lower the temperature of the extruder while printing.  This may be why the high temperature extruder did not come with a turbine fan.  Now you can print at high temperatures and cool your prints at the same time.  You will also not have to use the two M3 screws to hold this part in, although you can use them from the inside if you want.  You will also be able to remove the extruder with only two screws, and the the Maxflo helps align the extruder perfectly on the locater pins.  Occasionaly you may have experience the J hook bumping into taller prints, but with the Maxflo that is completely internal, that is no longer a problem.  This part has been extensively tested and gone through several redesigns to arrive at the perfect balance between fit and performance.