Most SPring-8 x-ray beamlines are installed double-crystal monochromators that are standardized. For x-ray undulator beamlines where power density of the beam are quite high, rotated-inclined double-crystal geometry is usually adopted, which enlarges the footprint of the incident beam on the crystal surface to reduce the power density. On the other hand, adjustable-inclined double-crystal geometry is adopted for bending-magnet beamlines to extend the available energy range with a limited Bragg angle range. The standardized monochromator mechanism is compatible to both of the geometries, only by changing crystal mounts. Detailed description of the monochromator mechanism is presented.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.