From Film Cyfrowy…
SmallRig BMPCC Cage: Best Price/Performance, lightweight, HDMI Lock, Locating screws.
Multiple mounting points on all sides allowing easy attachment of accessories. The battery door can open easily allowing access for SD card and battery changes.
It attaches to BMPCC’s top and bottom holes by two screws. Also 2 small locating screws on the top and bottom plates to lock the camera from twisting.
For more: SmallRig.