This is a cool macro accessory that mounts firmly to the camera body and works as a variable extension tube by turning the outside like a focus ring. It has a helical extension unit it it that makes an effective range from 22mm up to 68mm. Note that not all lenses will work throughout the whole range - most of the lenses with bay VI filter mount will work, but a few of the lenses with fat barrels will not. That said, all lenses will work at the maximum extension and close to it. I find it particularly well suited with the 80mm Xenotar, 120mm macro, and 150mm lenses. It will work with the 90mm macro, but not through the whole range.