This device supplants a monopod to allow the camera to stabilize on its own on a flat surface. The 3009 ballhead has a large 3/8"-16 threaded hole for excellent adhesion to the monopod, and will hold smaller 35mm outfits in most any position.
Note:The bottom of the 3422 has only a 3/8"-16 threaded socket; if you're using with a monopod with only a 1/4"-20 screw, you'll need a reducer bushing in between them.