A.
anwered by: isteinhoff
The WH-6700-R Freehub body exclusively is used on the WH-6700-G-R Hub, normally printed somewhere on the hub shell, which I have only seen on the Straight Pull style Ultra Hubs.
The FH-6700 is far more common, printed one the shell, like normal. If you have traditional J-Bend Spokes on an Ultegra 6700 hub, this should be your direct replacement.