This thing is composed by 5ea STLs.
Files "fan_stand_01_pylon.stl", "fan_stand_02_knob.stl" and "fan_stand_03_fitting.stl" must be printed twice.
I suggest to use a little bit of glue to attach the 2ea fittings to the holder (but it's only recommended, not necessary at all).
The vent just snaps into the holder (perhaps you will have to lower a little bit the retention fittings with a file but it works as it is anyway. It's guaranteed).
The fan I've used is a classic computer case fan (80x80x24.7 mm).