New Hejnar Photo Quick Release Screw-Knob 1.5 inch Arca Swiss type clamp with dual mounting ( 1/4-20 screw or 3/8-16 post) and captive style knob. Hard coat black anodized surface.. Combine clamp with my nodal slide base rails and you have rail with integrated clamp. You can mount two clamps together using aligning pins and bushing (sold separately). They can be mounted in different orientation. Pins will prevent clamp from twisting. Set ( two clamps ) can not be assembled with knob facing the same direction. When disassembled they work as standard arca swiss clamp. It is the best quick release system for tripods when combined with Arca style ball head.