Extend the reach of your telephoto lens with this APO Teleconverter 2x EX DG from Sigma for Sigma SA-mount cameras and lenses. This model doubles the effective focal length while only losing 2 stops of light in the process. It also retains communication between the lens and camera, allowing users to use automatic metering and autofocus. Additionally, this teleconverter has a multi-layer coating that reduces flare and ghosting for sharp, clear imagery.