Filament runout sensor embed inside the stock extruder of the Creality K1, K1 MAX.
This allows you too easily change filament. When filament is detected by the sensor that will trigger an auto load material function.
Since we don't use the rear filament sensor, the reverse bowden path is simplified. This allow an easier insertion of the filament inside it and with less drag. It's also much easier to relocate the spool anywhere you want, this is especially true for the K1.
The sensor works with TPU even if the reverse bowden is bypassed.
It also reduce the length of leftover when a spool ends as the sensor is super close to the extruder.
And it's useful to have a filament runout sensor inside the toolhead when you want to use a MMU (near futur proof ^^ ).

3d Model Link : https://makerworld.com/en/models/171973