Haoge 50mm Subtend/Bidirectional Double Dual Quick Release Clamp for Arca Swiss RRS Benro Rail Plate Nodal Slide The Haoge CP-50B Subtend & Bidirectional Clamp features double clamps that will fit any standard Arca-Swiss style quick release plate. The dual screw-knob clamps allow you to mount a QR plate on the top and bottom simultaneously, or mount the clamp to a multi-purpose rail and then mount a QR plate to the top so you can move your set-up along the rail without moving your tripod or camera support.