This is a simple 8" long 2.5mm audio cable. It is terminated with a 2.5mm audio plug on one side and unterminated with bare wires on the other end. These are to be used with the ModKit shields.
The 2.5mm plug is the same one used by many devices. A lot of older cell phones used this size for the headsets. It is the audio jack size generally used on a lot of portable electronics that didn’t use the traditional 3.5mm headphone jack. Also, the Rebel line of Canon dSLRs use this jack for shutter control. See the link below for creating your own
Note: This is not the more common 3.5mm (1/8") jack size. They will not work with 3.5mm jacks.