GR-874 connectors were a unisex series designed by the General Radio Corporation. GR-874 was designed for test equipment. By rotating one connector 90 degrees to the right or left, the inner and out leaves will mate with any other GR-874 connector. GR874 adapters and connectors can have a threaded locking collar which is also unisex as the collars can be backed up exposing threads for another locking collar to go over. Great in applications to ~8 GHz.