This is the bottom mounting plate to bridge the shoulder cut out of the camera. Screws into front of the body and locates in the shoe in the rear. This replaces your Steadicam dovetail . So it mounts directly. Lots of adjustment for different camera configurations. Plus (+) it will also work with the Red camera and you can remove the locating pin and mount it to the Sony Quick release plate. #CP003-U Alexa to Master/Ultra Steadicam Plate.