The Movcam 104:72mm Step-Down Ring for Clamp-On MatteBoxes lets you mount 72mm lenses onto 104mm clamp-on matteboxes -- the kinds without a thread on their rear adapter.

The ring is split along a point of its diameter to flexibly widen and mount a mattebox. (A locking pin on the side of the mattebox securely tightens the ring in place.)

Split Ring for Clamp-On MatteBoxes

Related Questions and Answers

Q: 1. I have a RRS BH55 ballhead with the 60mm LR (B2-AS II LR) plate on it now. I am contemplating buying the 80mm LR plate for the ballhead for use with my longer lenses and also for the extra locking length on my night sky and long exposure photography. I know this will fit, but I am assuming I will need the 3/8-1/4 reducing bushing to mount this plate to my ballhead stem? Will the interior threading of the bushing interfere with the mounting screw? The plates that come on this ballhead have unthreaded center mounting holes so the mounting screw just drops thru.

A: This clamp use a bolt that screws in and typically screws to the stem of a ball head. You will have to figure out what the thread size of your ball stem is and correctly match the head of the bolt to sit into the countersunk hole of the clamp. The center socket has female 3/8"-16 threads and it accepts metric 6 and 1/4"-20 threaded screws via a bushing adapter. If your head takes a 3/8"-16 bolt, that would be ideal, otherwise you would need a reducer.

Q: 2. i just acquired a set of gitzo series 5 systematic tripod legs. would i be better off with the rrs 60mm or 80mm lever release clamp?

A: RRS 60mm works with camera body well and 80mm it is more for long lenses with tripod caller

Q: 3. Hi,Will this fit a Gitzo GT2542T?

A: That is a series 2 Gitzo tripod, that center column is meant for a series 3. It will not fit.

Q: 4. Will this clamp fit on the Sacheler Ace M sliding plate?

A: Yes, the Really Right Stuff B2-LLR-II Lever-Release Clamp will fit on the Sacheler Ace M sliding plate.

Q: 5. Will this work with a novoflex magic ball?

A: It should is my guess. BUT. finger access under the mounting plate and ball handle might be an issue. Take it to a big camera store to check if it works. The huge issue with your ball head is- given the weight of the camera, is it good enough to clamp the load firmly?

Q: 6. Will this clamp fit on another brand Ball Head I have a Sirui?

A: I mounted mine to a FLM ballhead using the provided 3/8 to 1/4 x20. Works great

Q: 7. Does this B2-LLR-II come with the center bolt to mount to a BH-55.

A: Yes, an M6 screw and 1/4-20 screw are available inside the pack of the Really Right Stuff B2-LLR-II Lever-Release Clamp.

Q: 8. Can this be fixed on a Sirui L20S Monopod / Tripod head...?

A: Yes it will technically screw onto the top of the sirui baseplate but it will be off center.

Q: 9. Which plate is used to connect the pano gimbal to this leveling base in the second picture?

A: That would be the Really Right Stuff PG-02 LR Pano-Gimbal Head with B2-LR II Lever-Release Clamp.

Q: 10. Is it possible to swap the normal pan knob with the 15 degree pan knob? I try to keep on the ball head controls on the left.

A: Unfortunately, the FLM 47GX Centerball Tripod Head knobs cannot be swapped.