This X-844 is needed to mount the PhaseOne DF or Mamiya AFd-series digital camera to the X2-PRO system.
The X2-PRO with this combination excludes the use of the 28 Schneider Digitar, and excludes the use of X-231 and X-232 adapting lensboards for Hasselblad and Mamiya 645-ProTL optics.
The X-844 places the CCD exactly in the optical center of the lens, in horizontal as well as vertical position.