The 38mm Really Right Stuff B2-FAB Screw-Knob Clamp 38mmfrom Really Right Stuff B2-FAB Screw-Knob Clamp 38mmis an Arca-type compatible clamp with laser-engraved 1mm scales on each side of 38mm long jaws, so a camera can be aligned within the quick release.

The screw-knob style clamp features a rosette design for secure mounting to compatible ball head and other devices. A legacy tongue-and-groove adapter is available separately. A 1/4"-20 threaded female socket enables the clamp to attach to a monopod or tripod without a quick release. This clamp is constructed using black anodized aluminum.

Arca-Type Compatible Clamp    38mm Long Clamp    Screw-Knob Style Closure    Rosette Mounting Base    1/4"-20 Threaded Female Socket    Laser-Engraved Scale in 1mm Increments

Related Questions and Answers

Q: 1. What is the diameter of the top plate?

A: The manufacturer does not mention this information. This is a Arca Swiss mount so you will need a Arca style plate for compatibility. https://bhpho.to/3q0MG1v

Q: 2. I want to mount this on the top, moving rail of a Manfrotto 454 Macro Focusing rail to accommodate a l-bracket attachment of the camera body. Does the tightening knob clear the bottom of the clamp when mounted on a flat surface? Also, will the anti-twist tabs fit into the 1/4" slot in the 454 top rail?

A: Good question. Thank you. There is not enough clearance to accommodate functionality of the knob when attempting to mount it with the anti-twist tabs into the 1/4 20 slot.

Q: 3. Does the diameter of the shaft extend below the bottom plane, like some of the cheaper clamps that people have complained about?

A: The Really Right Stuff B2-Pro-II 60mm Screw-Knob Pro Clamp (B&H# REB2PROII) is made with exacting precision and it will fit the intended heads without having any problem like the one you mentioned: Really Right Stuff ball heads Arca-Swiss current model ball heads Manfrotto 468 ball head Manfrotto 468RC2 ball head Manfrotto 488RCO ball head Manfrotto 469 ball head Manfrotto 469RC ball head

Q: 4. Can this be used on the Manfrotto BeFree? Will the legs still fold properly?

A: With a reducer bushing purchased separately you can fit it on the top of the quick release plate that comes with your tripod but if you do that you will have two different clamps. You may end up sometimes opening the wrong clamp accidentally. If you want an arca clamp to a Manfrotto Befree tripod I would recommend this adapter from Manfrotto. If you use this you will only have one clamp. Please make sure your tripod head is listed as compatible in this listing. It is small and shouldn't affect the folding of the legs. https://www.bhphotovideo.com/c/product/1484861-REG/manfrotto_msq6t_top_lock_travel_quick.html

Q: 5. Is this compatible with Manfrotto MHXPRO-BHQ2?

A: You may consider purchasing the Desmond DBAD Female to Male Boss Adapter for Select Manfrotto Heads, B&H # DEDBAD, to connect the Really Right Stuff B2-Pro-II 60mm Screw-Knob Pro Clamp to the Manfrotto XPRO Magnesium Ball Head with 200PL-14 Quick Release Plate.

Q: 6. Can I mount this to a video tripod, like a Sachtler or Miller?

A: Whether you can mount the Really Right Stuff B2-Pro-II 60mm Screw-Knob Pro Clamp on your existing head will depend on the connecting method on your head. This clamp features one threaded 3/8"-16 recessed center socket flanked by two threaded 1/4"-20 recessed center sockets, the RS-Pro-II can be mounted from beneath directly on a tripod head platform, or from above using 1/4"-20 or M6 screws.

Q: 7. Can this be used on the Gitzo Mini Traveler?

A: The Really Right Stuff B2-mAS Screw-Knob Clamp with 1/4"-20 Screw (38mm) can be used with the Gitzo Mini Traveler.

Q: 8. Can this be mounted on a monopod. Then attach the wimberly monogimble?

A: The Really Right Stuff B2-Pro-II 60mm Screw-Knob Pro Clamp can be attached to a monopod. The Wimberley MH-100 MonoGimbal Head for Monopods has a 3/16"-16 threaded socket and an Arca-Swiss Style dovetail. You could use the TTS clamp, but it is not required to use the Wimberley MH-100 MonoGimbal.

Q: 9. How is this screw know compared to the lever clamp?

A: The screw and the lever are personal preferences, beyond that some users like the lever when they are shooting in cold weather and wearing gloves. The lever is much easier to use with gloves and is also quicker.

Q: 10. Thank you everyone for your response. But I'm still wondering: if I mount this on a flat surface, and that surface extends out past the bottom of the clamp (not to the knob, of course), does the diameter of the shaft allow for clearance so the clamp sits firmly on the flat surface? Sometimes I use clamps on something other than ball heads. Thanks again.

A: Yes, the bottom surface of the Really Right Stuff B2-Pro-II 60mm will seat flat on the camera support plate system similar to BH #PLPMPMT1009. However, the knob can not be under the same plate surface because it's larger than the clamp high. The knob is 25mm while the plate is only 18mm. I will recommend the BH #REB2LRII with the Level since this part is the same high as the clamp and won't interfere if you place your plate on a flat surface.