New Hejnar Photo Quick Release Screw-Knob 1.5 inch clamp set. Using provided pins clamps can be mounted back to back in different orientation. Pins will prevent clamp from twisting . Set can not be assembled with knob facing the same direction. When disassembled they work as standard arca swiss clamp. Hard coat black anodized surface. It is the best quick release system for tripods when combined with Arca style ball head. Combine camp with rail and you have rail with integrated clamp. Great addition to your equipment for fraction of the cost.