Sigma USB Dock MICRO TUNE, CUSTOMIZE, AND UPDATE YOUR LENS Update Lens Firmware Customize: Autofocus, OS, Focus Compatible with Global Vision Lenses (except DN lenses) The Sigma USB dock works in conjunction with Sigma Optimization Pro software in order to connect a photographers lens to their personal computer to update firmware and other parameters such as focus, and for the Sports category: Autofocus speeds, focus limiters, and optical stabilization functionality. Updating the firmware can be done via the internet. Sigma Photo Pro is available for Mac and PC computers. Focus Settings: 4 Categories of customization for fixed focal length. 16 Categories of customization for zoom lenses (4 options for focal length) x (4 options for shooting distance). Sports Line: AF Speed: 3 adjustment modes. Focus Limiter: Customize auto focus range. OS: 3 adjustment modes.