1) Expand for USB port,supply up to 500mA current per port. 2) Adopt the second age USB controller. 3) external power supply Features: 1) Driverless.hot plug & play 2) Internal over current protection circuits. 3) Suppot USB 1.0/1.1.Compatible USB2.0,full speed up to 12Mbps 4) Design with super streamline & mini 5) Suppot OS:Win95 OSR2/98SE/ME/2000/XP,Linux2.4 and Mac OS8.5 or over version 6) Chains up to 127 USB drives.