I could not measure the speed of the adapter, as larger file transfers after 150 Mbyte broke the power supply and the adapter includes external hard drive reset. This happened every time and regardless of whether you pocketed the extra power cable or not. I was worried about the data on my (actually highly reliable) WD HDD. The (not) transmitted data were certainly unreadable after the transfer attempt. In addition, the adapter is very loose in the ExpressCard slot, so you almost always mitherauszieht adapter when unplugging the USB device or the power supply. Perhaps the adapter on other systems work better, but owners of a Dell Latitude E6520 I advise definitely the purchase.
