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. This Autofocus Extension Tube Set (10/16/21mm) for Sony from Micnova contains three tubes of different length, a 10 mm, 16 mm, and 21 mm, which can be used individually or in any combination to obtain the desired magnification. These tubes allows you take close-up photos using your Sony E-mount lens and lenses by placing one or more of these autofocus extension tubes between the camera body and the lens. The back of each hollow extension tube has a Sony E-mount so that it attaches to the camera just as a lens would, and the front accepts a Sony E-mount lens. With metal construction and lens mount index, it can work with telephoto lens tightly, and mount the lens easily. The front and rear caps prevent the dust into the tubes. Designed with all the circuitry and mechanical coupling, these extension tubes are able to maintain autofocus and TTL auto exposure normally. The extension tubes have no optics. By moving the lens closer to subject this way, you get a magnified image. The greater the length of the extension tube, the closer the lens can focus.