This is a used item that has been tested and is in working condition. It can be attached to Nikon F-mount lenses to double the focal length of telephoto lenses, but it will result in a two-stop reduction in light. This is a set of two. There are signs of aging, such as dirt and scratches on the lens barrel, but there is no clouding or mold on the lens surfaces. There is some dust inside. It is only compatible with manual lenses, and it is recommended to use it with a camera body that has an exposure meter coupling lever. Price negotiations are welcome.