This is a filament runout sensor housing for the QIDI runout sensor. Placement on XMAX is far from ideal. This moves it to the top cover for a better feed angle.
Disassemble the sensor casing (torx screws I believe) and place it in the housing. Make sure the lever isn't hung up. Use the two original board screws to attach. Slip the cover on and insert into top cover.
Supports required for Touching Buildplate only. You'll almost certainly have to extend the wiring harness to reach the new location, at least on the MAX.
The author remixed this model.