This Rolux cable RL-C5 is provided with a 4-pin XLR female connector and on the other end with a D-tap male plug.
Application Rolux 4-pin XLR Female plug with D-Tap Male RL-C5
By using this cable you can connect devices with a 4-pins XLR connector, such as a Blackmagic Studio camera, to your V-Mount battery via the D-tap connector. This allows you to supply your device with power.