A solder fume extractor for rectangular 120mm fans. 4x M5x20mm screws are needed to assemble the hinges. If needed, the fan can also be screwed in place with 4x M4 screws, but the fit should be very snug already.

Model in the picture was printed using eSun PLA+ with a 0.4mm nozzle using a Bambu Lab P1S.