This adaptor lead is fitted with a JST BEC socket at one end and a JR/universal RC plug at the other end. It is great for powering RC with 2S LiPo voltage directly from a 2S LiPo battery. Most receivers are fine on 2S LiPo voltage but make sure any servos connected are HV or WV types.
Another benefit/use for this lead is to act as an on/off switch for the RC system. Plug in the battery to fly, and unplug it at the end of the session. No moving parts. Nothing to fail. Minimum weight.
Never attempt to plug a JST BEC plug directly into a receiver as even a momentary incorrect contact will burn out all the servos.