Viltrox C-AF 2X Teleplus is made of high-quality coated optical glass with optical design. It can make the focal length of all the Canon EF lens increased to 2 times as respectively, and the auto-focus function of the original camera lens can be used perfectly, and does not change the Exif information. C-AF 2X TELEPLUS specifically use for 100mm or more fixed focal length lens, such as 300mm f / 2.8 lens, and 200- 500mm long lens perfect combination, can be used for fixed focus lens and a telephoto lens, but is not recommended for use in less than 60mm of short-focus lens.