This aluminium 20 mm opening carabiner has a D-shape to make the connection easer and to better position it. Automatic locking system: ideal for frequent use Three step unlocking: turn the ring, push it down and then push to open the carabiner The carabiner is an essential part of any fall prevention system. It is designed for use as the connection between the various system components or to connect the various components to the work structure anchor point.