The STC-I015 USB 3.0 A Male to USB Female for External Hard Disk with Extra Power, Black USB 3.0 Male to Dual USB Female Extra Power Data Y Extension Cable for 2.5" Mobile Hard Disk, Two USB female connector, One is for USB 3.0 power and data, another one for USB 2.0 power only. Does one USB port not supply enough power for your USB device? Our Sync USB 3.0 Power Adapter Y cable for you is the solution. Our cable allows for power to be taken from 2 USB ports, like a PC and an External hard drive. Allows you to link 1 USB device into 2 USB Ports on your PC for more power. There are times you may have an external device, such as a portable 2.5 hard drive, and a standard USB cable is not able to transfer enough power to operate the device.