This is the cable designed for the encoder that is pre-attached to the NeveRest Series of motors and gearmotors. It has a connector on the opposite end to directly interface with the REV Expansion Hub or the REV Control Hub.
2019 Update:
The 'a' version of this cable as the encoder channels swapped so that the encoder counts in the same direction as the output shaft spins. This simplifies the usage of the encoder with the various programming languages for FTC!
Specifications