1) Expands four USB port supply up to 550mA current per port 2) Uses a second generation controller 3) No external power supply necessary 4) Driverless, hot plug and play 5) Internal over current protection circuits 6) Support USB 1.0/1.1, USB2.0, full speed up to 12Mbps 7) OS Support: Windows 95 OSR2/98SE/Me/2000/XP, Linux 2.4 and Mac or over 8) Chains up to 127 drives 9)Size: 8*4.2*2.5 cm