This allows you to mount a Yaesu FTM-400XDR or FTM-400XD control head to a Ram Mount. It provides a 1" ball along with the appropriate hardware to adapt the ball to the back of the display head.
Those you familiar with this unit know its not the standard ball mount thread on the back of the unit and the mount that comes in the box is really flimsy. I also don't like how the X-grip mounts work with this head. There are other mounts out there, but none as secure and clean as using a Ram Mount system.
ALSO FITS - Yaesu FT-891