These adapters have an "F" female jack on one end and either an RCA male plug, RCA female jack, or a BNC male plug. Keep a selection of these around because you never know when they will come in handy.
We use a lot of the F-Female to RCA-Male adapters for video and audio signals that are running over coax. It's easier to put a standard F connector on the coax, then use an adapter to go to RCA, then plug into the subwoofer or amp than it is to try to put RCA connectors on the end of coax.