This thing is a nozzle for a small radial blower.
Attach to your K8200 in order to keep the extruder tube cool during long prints.
An axial fan could also work here but a 40mm fan is too large and smaller ones are difficult to get. In my opinion the radial fan also fits better behind the extruder and is easy to mount with a few cable ties.
Adjust dimensions in OpenSCAD or Customizer then print with perimeters only ( zero infill and no top/bottom layers ).
Use glue to attach the nozzle to the blower and cable strips to hold the blower in place.
I also recommend getting a fan regulator ( FAN MATE 2 or similiar ) because operating the blower at about 7 Volts seems to be optimal.