This is another extruder rotation indicator. FIts to the Prusa i3 mk2s or mk3 extruder.
Glue a 8x3 mm magnet with some super glue onto it and snap it on the motor.
Based on the idea of Petclaud:
https://www.thingiverse.com/thing:2638857
Category: 3D Printer Accessories
The author marked this model as their own original creation. Imported from Thingiverse.