The docks are slightly different. The USB and HDMI connectors are rotated 180 degrees. When the Atrix came out it was rumored that the docks used magnets to let the phone know the difference between dock types. That is not true, the circuit in the dock does. I was able to modify my Atrix car dock to work with my bionic, it took the drimil to make it happen, and the plugs had to be rotated. The distance from the bottom of the phone to the 2 ports is the same, but the Bionic is taller. Also the space between the USB and HDMI is the same. Hope that info helps.
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