This part fits the following other parts:

#27478 - Sonic 540 SP5 25.5T Brushless Motor

#27479 - Sonic 540-SP5 21.5T Brushless Motor

#27480 - Sonic 540-SP5 17.5T Brushless Motor

#27481 - Sonic 540-SP5 13.5T Brushless Motor

#27482 - Sonic 540-SP5 10.5T Brushless Motor