This is a high quality switching AC to DC 5V 3000mA Barrel Jack wall power supply.
These wall adapters are perfect for supplying power to many single-board computers like the pcDuino, Beaglebone Black, or the Raspberry Pi. Please note, this specific supply (5V/3A) is also FCC/CE certified and works with 100-240VAC inputs and has a Center-positive 5.5x2.5mm barrel connector.
Product image for illustration purposes only. Actual product may vary