Tamron SP Flat Field 2x Teleconverter (Model 01F) is a compact, six element optical wonder that doubles the focal length and magnification ratios of your Tamron Adaptall lens. Designed to fit your lens and Tamron adaptall mount, full AE or TTL capabilities of your camera are maintained. The flat field optical design minimizes off-axis aberrations; spherical and chromatic aberrations are also extraordinarily well controlled. Superior performance is achieved with the flat field converter.