A thing that serves two purpose!
It's a runout filament sensor and it's also a great filament guide with bearing!
Super easy to assemble. No fasteners!
I added the Fusion 360 file. Be warned though, I went through many iterations and it's a pretty ugly timeline! Good luck!!!
How to connect and activate the filament runout sensor is an other matter and I won't cover it here. Good videos can be found on Youtube. Just note, that it can be done connecting directly to your Ender 3 board or to the Raspberry Pi if you have OctoPi installed. Google it! :)
By the way, if you installed Octoprint, you should definatly check out an other thing I made, the Octo Duct (https://www.thingiverse.com/thing:3329293).
Hope you like it!
Amazon Basic PLA
Clean print without support material.