Doubles Focal Length of Lenses (4-Elements) Multi-Coated Optical Glass with Anti-Reflection Coating NOTE: Not compatible with Canon EF-S Lenses - Only EF Lenses) ** For The Same Extender which is applicable for the EF & EF-S Lenses - SEE ASIN: B081TNW121 ** Manufacturers' Lifetime Warranty Item Includes: Case, Protective Lens Cap, Nw Direct Micro Fiber Cleaning Cloth 2x (Doubler) 4-element bayonet mount Teleconverter multiplies the focal length of any fine optic it's used with by 2x, maintaining the resolution and contrast at a high level.