The Canon Tripod Mount Ring D for IS 100mm F/2.8L Macro Lens is designed for the new Canon 100mm f/2.8L macro lens with Image Stabilization. The ring holds the lens more securely than if the camera is mounted on the tripod. Made of a lightweight metal that matches the color of the lens (black), the mount ring is very helpful in extreme close-up photography, where the slightest vibration will show up in your photo.