In 2013 Sigma introduced our Global Vision lens line along with the USB dock, an accessory sold separately allowing you to calibrate the AF Data of any Global Vision lens. By connecting the USB cable to a computer, SIGMA USB DOCK enables photographers to update the lens firmware and adjust parameters such as focus. The adjustment is processed with special software (SIGMA Optimization Pro). The AF speed, focus limiter and OS function are also customizable for Sports lenses. To find out more information, consult the USB dock page.