This is a Multi-Purpose Rail. Really Right Stuff makes Multi-Purpose Rails in a variety of lengths, from 73mm to 192mm (2.4-inches to 7.6-inches).

1. Use as a lens plate for a collared lens.
2. Use as a camera body plate for some medium and large format cameras.
3. Add a clamp to the rail and use use as a nodal slide for panorama photography.
4. Attach to the bottom of any object to mount in a Really Right Stuff clamp.

Specs:

1. Length = 73mm / 2.9"
2. Width = 38mm / 1.5"
3. Weight = 1.5oz / 44g
4. Includes one B102 mounting screw, 4 caphead M3 screws, one MPR-C optional flange, and hex keys for installation.
5. Compatible with all Really Right Stuff and Arca-Swiss-compatible quick release clamps
6. Moveable anti-twist flange can be mounted in eight different positions in the MPR-1.
7. Accepts Really Right Stuff and Wimberley flash brackets
8. Standard Really Right Stuff 5-year warranty
9. Price = $55