The Fotga automatic macro Extension Tube Set 13+20+36mm DG II is 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. The extension tubes have no optics. They are mounted in between the camera body and lens to create more distance between the lens and film plane. By moving the lens father away from the film or CCD sensor in the camera, the lens is forced to focus much closer than normal. The greater the length of the extension tube, the closer the lens can focus. It comes as a set (13mm+20mm+36mm). It contains 3pcs tubes in different length 13mm/20mm/36mm,which can be used in any combination or individually. Each Tube has electronic contacts, which make it support automatic focusing, automatic exposure,etc. A 1/4? screw mount on 20mm tube. Diameter of the tubes: Approx. 62mm Tube length: 13mm,20mm,36mm Material: Metal Suitable for: All EOS EF / EFS lens and camera with EF/EF-S mount Package includes: 1 x Fotga automatic macro extension tube 13mm+20mm+36mm set 1 x Front cap 1 x Rear cap