Phase reverse connectors - used with stereo balanced connectors - usually professional recording.
I have a number of these - so I could offer a job lot price - how many ?
Phase reverse is 180 degrees difference between left and right stereo signals.
Neutrik 3 pin XLR male to female connectors - pin 2 crossed over to pin 3 and pin 3 crossed over to pin 2.
Useful sometimes to correct a strange multiple microphone sound. Cable lengths 20 CM.