This adapter is designed specifically to provide 5.25V not 5V, but still call it a 5V USB adapter. The purpose of this transformer is to solve a problem that often occurs with USB-powered devices draw so much current that the cable resistance causes a voltage drop, so instead of 5V, the device actually receives 4.75V or less. To avoid this problem, we have created this transformer handy with 5.25V output.
In addition to providing a stable voltage of 5.25V, this transformer delivers up to 2 amps of current, which is great for use with your Raspberry Pi, Cubieboard, BEAGLEBONE, PcDuino, cards etc.
Note: This source operates with an input voltage of 100-240 VAC.