The DJI Zenmuse H3-3D mounting adapter for phantom is used when upgrading from the H3-2D To H3-3D gimbal. This mounting adapter is needed on Phantom bought before March 2014, the Phantom shell had a modification from mid March onward. If you have a small rectangle cut out on the underside of the Phantom this adapter plate will be needed. Later Phantom's have a larger opening to allow the H3-3D yaw motor to clear the body.