The RRS-9000444 Multi-Purpose Double Dovetail accepts Arca-Type clamps on the top and bottom, and has three applications. It can be used as a balancing rail for a DSLR camera on a RRS FH-350 Fluid Head, as a platform for RRS flash rings with non-collared lenses, or as a nodal slide for RRS panorama gear. Really Right Stuff Multi-Purpose Double Dovetail Nodal Slide 5.7"/145mm Rail w/Integral Clamp RRS-9000444