This is a cage for Blackmagic Micro Cinema Camera/ Blackmagic Micro Studio Camera. 

The cage is made from the high quality aluminum, so the cage is lightweight and it can matched to your camera perfectly. With two screws on the bottom to mount camera and make the camera stable when you're shooting. 

There is a NATO-style side rail and two cold shoe mounts which can mount more accessories. Besides.

There are some more info links to the specification of the cage:

Product Features:
● Made from one piece of aluminum
● Two cold shoe mounts
● NATO-style side rail
● Mount camera with two screws
● Combination with the HDMI Cable Clamp 1693 which can protect the HDMI

Compatibility:
Blackmagic Micro Cinema Camera
Blackmagic Micro Studio Camera 4K

Includes:
1x Cage
2x 1/4”-20 screw
1x Hex Spanner

Net Weight: 190g
Product Dimensions (L X W X H): 85.3x98x69mm
Material: Aluminum Alloy

It is call SMALLRIG Blackmagic Micro Cinema Camera Cage. Very happy to share with you for info.