When a standard USB cable cannot transfer enough power to operate an external device, such as a portable 2.5in hard drive, you need a USB 2.0 y-cable. Simply plug this cable's USB B end into the device, and then plug the two USB A ends into open USB ports on one PC or Mac. This cable then pulls power from both USB ports, and thus increases the output to the external drive. The red molded hood on the auxiliary USB A connector enables the user to quickly distinguish between main and auxiliary power. Foil and braid shielding reduces EMI/RFI interference, and twisted pair construction reduces crosstalk for high speed, error-free data transfer. This cable is compatible with USB 1.0, 1.1, and 2.0 specifications.