Sigma 879101 1.4X Teleconverter Canon EF BundleExtend Your Reach with Superior Image Quality The Sigma TC 1401 1. 4x Teleconverter is designed to increase the focal length of your Canon EF mount lenses while maintaining exceptional image quality. Optimized for Sigma's Global Vision line, this teleconverter offers full communication between the lens and camera, allowing for autofocus operation and reducing chromatic aberrations. Key Features: 1. 4x increase in focal length for Canon EF mount lenses