This cable is kinda fascinating - it has an integrated boost converter, so you can plug it into any USB port (from a computer, battery pack, etc), and it will give you a higher DC voltage! It's a handy way to power a 9V or 12V device. Unlike our other 'USB booster' cables, this one comes with a fancy lil display and a switch so you can select between 9V or 12V output and the voltage will be indicated. You can draw about 1A from 9V setting or 750mA from the 12V setting.
The cable comes with a 2.1mm inner diameter (5.5mm outer diameter) DC plug, arguably the most common, but also includes a 3.5mm / 1.35mm adapter.