Optical filament runout sensor - Work with all the filaments!

Very simple but functional concept for all the filaments 1.75mm diameter, using an optical endstop and the gravity force.
This system also works with transparent filaments because using a fall knob, Newton doesn't fail.
Just insert the filament without the knob inserted in its housing, then insert it so that it rests on the filament.
When the filament comes out the knob will fall due to gravity, activating the optical endstop.
The two fixing holes are for profile 2020, obviously this thing i