For the macro photographer
Extension tubes are designed to enable a lens to focus closer than its normal set minimum focusing distance. Getting closer has the effect of magnifying your subject (making it appear larger in the viewfinder and in your pictures). They are exceptionally useful for macro photography, enabling you to convert almost any lens into a macro lens at a fraction of the cost while maintaining its original optical quality.
Maintain autofocus and TTL exposure
Kenko DG AF Extension Tube Set 12-20-36 Kenko's Auto Focus extension tubes are designed with all the circuitry and mechanical coupling to maintain auto focus and TTL auto exposure with most Canon, Nikon, and Minolta lenses given there is enough light to activate the cameras AF system properly.
What's in the box?
The Kenko DG Auto Extension Tube Set contains three tubes of different length, a 12 mm, 20 mm, and 36 mm, which can be used individually or in any combination to obtain the desired magnification.