This XPRO Magnesium Ball Head from Manfrotto features an integrated Arca-type clamp and a MSQ6PL Quick Release Plate. Arca-type compatible quick release plates such as the MSQ6PL can be attached or removed from the Arca-type clamp located at the top of the ball-and-socket joint by tightening or loosening the clamp's locking knob. Within the recessed surface between the clamp's jaws is a retaining pin. This pin prevents an installed quick release plate from accidentally sliding off when the clamp is opened.