These DC Plugs are perfect for powering Arduino Uno and Mega boards (use male cables as the boards have female connectors).
They come with a ~15cm long cable with ends pre-stripped and ready for soldering to your circuit board. One of the two wires is coloured with white stripes, indicating the +ve terminal.
We use ours for prototyping circuits, coupled with the DC Power Supply. We also recommend double checking the wires with a multimeter for continuity before use.