This adapter allows you to connect a barrel jack connector to bare wires. One end has screw terminals and the other has a 5.5x2.1mm, center-positive male barrel jack. If you need to connect bare wires to a barrel jack on an Arduino or a development board, this might be the simple solution.
With this Power Jack, you can feed various power source to your Arduino project, from 9V battery to 6xAA battery. A sample use is illustrated below.