This is the SMA coax connector and adapter group. The adapters can be useful for connecting shorter cables to make longer runs or connecting cables with non compatible ends. The SMA male to RP SMA female adapter for instance, can be used for connecting Taranis D antennas to the Taranis E. Many of you have been asking for that one. As with all of the RC Connector gear, the build quality is very good and the price more than reasonable.
To help and avoid confusion, here is a chart that shows the different configurations of the SMA and RP SMA connectors.