This high quality automatic macro Extension Tube Set 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 at a fraction of the cost while maintaining its original optical quality. | The DG 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 to obtain the different magnification. | It is with electronic contacts,which make it support automatic focusing,automatic exposure,etc. | The 20mm & 36mm tube are designed with 1/4" tripod mount. And it also comes with 2 caps (front and rear caps) to protect the mounts.