Viltrox C-AF 2XII TELEPLUS can make the focal length increased to 2 times,and the auto-focus function of the camera lens can be used perfectly, and don't change the EXIF information. C-AF 2XII specially use for 100mm or more fixed focal length lens, but not recommend for use in less than 60mm of short-focus lens. Features: Replacement for Canon EF-Mount 100mm and above Lens. (Perfect for 200 ~ 500mm lens, lens under 60mm is not recommended.) Can increase the lens focus length to 2 times. Support lens' AF function (Auto Focus) and won't affect to Exif information. Adopt 7 optical glasses, 4 groups, the depth of field is half of the lens. Good helper for long distance photography. With upgraded USB firmware interface. Specifications: Brand: Viltrox Model: C-AF 2XII Mount Type: For Canon EF-Mount Lens Magnification: 2X Depth of Field: Half of the Lens Min Stacking Focal Length: Equal to the Lens Constitution of the Lens: 7 Glasses, 4 Group Focus Mode: Full Auto Focus Lens Coating: Multi-coated Exposure Factor: Appro. 4 Times (Equal to 2 aperture) Item Size: 6.7 * 6.7 * 6.7cm / 2.6 * 2.6 * 2.6in(With front & rear cover) Item Weight: 159.5g / 5.6oz Package Size: 9.4 * 9.4 * 9.1cm / 3.7 * 3.7 * 3.6in Package Weight: 210.5g / 7.4oz Package List: 1 * Teleconverter Lens with Front & Rear Covers 1 * User Manual(English/Chinese) Note: Camera and lens are not included.