The Movcam 130:80mm Step-Down Ring for Clamp-On MatteBoxes lets you mount 80mm lenses onto 130mm 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. Does this item includes any screws or mounting hardware other than the Clamp itself?

A: The Really Right Stuff B2-LLR-II Lever-Release Clamp (80mm) (B&H# RERELESECLMP) does not include screws nor mounting hardware. Its center socket has female 3/8"-16 threads and it will also accepts metric 6 (i.e. M6) and 1/4"-20 threaded screws via a bushing adapter when mounting to a ball head stem. An additional two 1/4"-20 threaded holes are spaced 45mm apart from the center socket.

Q: 2. 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: 3. Can this be fitted on a Sirui L- 20S ...?

A: It technically can but it will be off center when you screw it onto the sirui basplate.

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. Hello, will this clamp fit on my Oben BZ-226T ballhead ? Thank you

A: Yes if you just use an allen/hex key to unscrew the plate on the ball head, then you could replace it with this RRS B2-LLR-II.

Q: 6. Will this replace the top of my Arca P0 Monoball? And if so how do you control the rotation? (the current plate has a screw to adjust tension on the rotation. thanks

A: yes you can replace the top with this unit

Q: 7. Can I screw it to my manfrotto 410 geared head?

A: You may use the RC4 plate included with the Manfrotto 410 to screw into the bottom of this RRS clamp, in order to use an Arca type plate.

Q: 8. Will this fit the Manfrotto 498RC2 ballhead using the Desmond DBAD Female to Male Boss Adapter for Manfrotto Heads?

A: Hello, yes the Desmond adapter will work on the Manfrotto 498RC2 and the RRS plate RERELESECLMP.

Q: 9. 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: 10. what are the proper dimensions for the plate that can go on this?

A: The Really Right Stuff B2-LLR-II Lever-Release Clamp works best with RRS plates that are 2.9" or longer.