This cord is very handy when you want to supply DC 5V into a barrel jack - since just about everyone has at least one USB charger available.
You can use this cord to power Stereo VU Meter from any USB ports. A standard USB plug on one end, and 5.5mm O.D. x 2.1mm I.D. barrel plug (center positive) on the other end. About 3 feet long.