This looks like a SeaLife Flex-Connect arm with ball joints on each end, although they make a GoPro adapter for it as well.
Direct light where ever you need it Expand your underwater camera set with one “click!” - The Flex Arm allows for creative lighting, easy aiming, and reduced backscatter by positioning the flash or light farther away from the camera. Each arm has 100° bending motion and adds 7” of length. The...
www.sealife-cameras.com
Easily build your underwater camera with just a "click" The new Ball Joint Adapter for Flex-Connect connects any brand of underwater light that uses a standard 1”/25mm ball joint mounting system to Flex-Connect arms, grips, trays and cold-shoe mount. This heavy duty aluminum piece is built for...
www.sealife-cameras.com
Mount your action camera to Flex-Connect accessories Use this adapter to mount your GoPro® camera to the Flex-Connect Cold Shoe Mount (SL991), Flex Arm (SL9901) or Handle (SL9905). Ideal for mounting a GoPro® camera over your SeaLife DC-series or other underwater housings with standard cold...
www.sealife-cameras.com
You can also mount it directly on the cold shoe without messing around with butterfly clamps:
An ultra compact setup Use the Flex-Connect Cold Shoe Mount to mount a light or flash directly to the cold shoe of your underwater camera for an ultra compact lighting solution. Combine with the Flex-Connect Adapter for GoPro Cameras to mount a GoPro directly above your underwater camera in...
www.sealife-cameras.com