The USB standard a drive relies upon to connect to your devices will determine a number of things about its potential performance, including maximum transfer rate. For instance, the transfer ceiling for USB 3.0 is theoretically ten times higher than 2.0. Letters following a USB designation (like USB-A, USB-B, or USB-C) indicate the physical type of connection; USB-A is the familiar rectangle most associated with the standard, while USB-C is a reversible flat oval.