The ProMediaGear PXC1 6-inch Arca-Swiss Type Nodal Rail with Integrated Clamp has a double dovetail plate. It can be clamped and be used as a macro focusing rail. Besides that, it can also mount other accessories alongside its top plate. The double dovetail is 3.5-inches long with an integrated Arca-Swiss clamp at the end. This mounts a camera at a crosswise position. This nodal rail has laser-engraved center lines for you to use as a guide. The knob is just the perfect size too. It is not too large or not too small and is easy to use in any condition. The PXC1 is made of a single T6061 aluminum. It is CNC machined and is lightweight and durable. It can surely carry any modern DLSR or mirrorless camera.