The AF Extension Tube Set can transform your Lens into a Macro Lens. It moves the lens from the film or digital sensor. The closer the focus is, the greater the magnification. The extension tube does not affect image quality as there is no optics inside. In comparison, a close up filter is often blamed for degrading the quality of image.
This tube set contains three piece tubes of different length -- 13mm, 21mm, and 31 mm -- which can be used individually or in any combination to obtain the desired magnification. These extension tubes are designed with all the circuitry and mechanical coupling to maintain auto focus and TTL auto exposure with most Canon lenses, given there is enough light to activate the cameras AF system properly.