This Auto Extension Tube Set for Canon (12/20/36mm) from Dot Line allows you take close-up photos using your Canon DSLR and lenses by placing one or more of these auto extension tubes between the camera body and the lens. The back of each hollow extension tube has a Canon mount so that it attaches to the camera just as a lens would, and the front accepts a Canon lens. By moving the lens closer to subject this way, you get a magnified image. Using these tubes, the camera's autofocus, auto exposure and TTL modes will function normally. You can also use any combination of the three tubes for varying degrees of magnification. Set includes a 12mm, 20mm, and 36mm auto extension tube.