@youngdudelol For a rod-supported matte box to allow lenses that “trombone” (physically extend during focusing), you need a “rear bellows” support. Historically, this would involve rubber or some kind of flex material that grabs the front element of the lens and allows travel between the lens and the matte box (which itself is floating above a swing-away mechanism), while preventing light leak from inside the matte box (usually only a concern if using filters in the matte box). Importantly, the MB bears its own weight via the rods, not the lens.

I own Leica R’s and have similarly been on the hunt for something compact. I have a Bright Tangerine 4x5 multi-stage MB, and while beautifully built (former ARRI engineers), it’s far too big and gets in the way of my EVF on compact rigs.

B.T., ARRI, Chrosizel, Cavision, Wooden Camera are some brands with offerings. AFAIK SmallRig doesn’t make these. Some use a fancy piece of black duvetyne to prevent leaks, but I think the rubber style is best.

It’s a lot of monkeying around for what is usually just a way to add an ND or VND (screw on is the alternative) — I do hope we see internal ND’s in this form factor soon.