On backorder, unknown ETA.
The filament monitor consists of a PCB which senses the rotation of a diametrically magnetised magnet. That magnet is in turn rotated by the filament motion via a hobbed part. The detected movement is transmitted to the Duet 2 Wifi, Duet 2 Ethernet or Duet 2 Maestro which uses the indicated movement to determine if the filament has run out, jammed or been ground away in the extruder. It is available for 1.75mm diameter filament only.
The monitor comes fully assembled, with resin printed housing. Please see the documentation for more information: Documentation for the Duet3D Magnetic Filament Monitor.