This is a design by Chris Riley or BrotherChris. He designed this to be a indirect sensor for runout detection on the Prusa MK2.5. I loved the design and brought it into Fusion. I changed the size of the Ball Bearing from 10mm to 7mm (same size Prusa uses), I also adapted this thing to mount on the SeeMeCNC EZR Extruder.
Lastly I changed the internal path for the filament. It has a chamfer to aid in retraction after the sensing is triggered.
Thanks Chris Riley. Thanks to Keegan! Thanks to Design Prototype test for the Duet Adaptation.