Torqeedo magnetic key for 402/403 Ultralights, Cruise R and the 503/1003 motors.
A spare is a great idea as we forget the key at home, lose the key, or forget to clip it to our PFD. Feces occur!
Helpful hint, please clip or tie off your key to your person or PFD. If you should fall out while running, or hit the throttle while dumping, you will watch your kayak sail off into the sunset without you!!!