Designed for use with any of the standard, telephoto, or zoom lenses, this converter doubles the focal length of the basic lens. Initial apertures are reduced by two f/stops. Sophisticated optical design enables the 2x extension with almost no reduction in image quality. An advantage is that the minimum focusing distance of a lens will not change with the 2x converter fitted - allowing for higher magnification.
Note: I have several of these used for significantly less than new