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 - particularly the lenses with fat barrels, but all lenses will work at the maximum extension. 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.
This copy is in excellent shape and fully tested for operation. Both the body cap and the rear cap are included.