Application: Provides 5V DC from USB, Power devices from a USB to 5.5 x 2.5mm port For small electronics and appliances which use a 5.5 x 2.5mm barrel jack for a power cable. Provides 5V DC from USB, Power devices from a USB to 5.5 x 2.5mm port For small electronics and appliances which use a 5.5 x 2.5mm barrel jack for a power cable.