Engine cut sensor on derailleur.
This sensor, which connects directly to the motor's yellow output, allows you to switch off the motor automatically when you change gear, so you can avoid banging your chain on the chainrings!
This addition to our kits is the ideal solution if you want to preserve your derailleur, when you change gear a motor cut occurs!
If your derailleur cable is frayed, you should get the version with derailleur cable, because the cable passes through the sensor and frayed cable will make it impossible to pass the cable through!