All of these universal wall mount brackets listed on the page below are compatible with Sony XBR-55X850C 55" 4K LED Displays. All Star Mounts carries various types of mounting bracket solutions such as flat (fixed position), tilting and articulating (full motion, pivot, swing).
Sony XBR-55X850C wall mount bracket requirements:
Fit VESA 300x300mm mounting holes on back of the TV
Support 43.8 lbs (weight without stand)
TV dimensions: 48.6" x 28.4" x 2.4"
Note: As always when attaching a bracket to the wall make sure that the structure attaching the wall plate to can handle the load being applied to it based on the wall mount style you choose to purchase.