These are the printed parts for the Duet3D prototype Laser Filament Monitor described at https://duet3d.com/wiki/Duet3d_Filament_Monitor:_laser_version. They must be printed in black plastic. I suggest 0.2mm layer height.
You can use Customizer to adjust the height of the centre of the filament above the PCB for optimum detection by the laser. Choose a multiple of your layer height. We have not yet determined the optimum value for this, but 6mm seems to work well with 1.75mm filament.
You can also adjust the diameter of the hex clamp for the PTFE inlet and output tubes. 4.6mm is about right for 4mm OD PTFE tube.