« Previous page X2-PRO system for DSLR : X-813 : X-813 X2-mount for Canon 1Dseries Mk 3 This X-813 is needed to mount the Canon 1D-series Mk 3 SLR to the X2-PRO system. (1D Mk3, 1Ds Mk3) The X-813 places the CCD exactly in the optical center of the lens, in horizontal as well as vertical position.