Two USB 3.1 Ports PCI Express with Low Profile Bracket, PCIe bus powered, support Windows, Mac upto 10.10.x and Linux USB3.1 dual ports @ 10Gb per port, Compliant with USB3.1 3.0 nd 2.0 Spec. PCIe bus powered, NO NEEED for EXTERNAL POWER SOURCE Compliant with eXtensible Host Controller Interface specification Revision 1.1 Compliant with USB Attached SCSI Protocol Revision 1.0 Support USB3.1, USB 3.0 and USB2.0 Link Power Management