The Sea & Sea Sea Arm 8 Ball Clamp is part of a line of modular accessories for underwater housing of DSLR cameras. The SA8 system is intended to connect an external strobe to an underwater housing for a DSLR camera.
The ball clamp is designed to secure two ball joints, and thereby connect two system components. These components might be a Sea Arm 8 Double Arm and a Slide Ball Base, or a Double Arm and a Strobe Head. These are, of course, but two examples of any number of possible system configurations.
The ball clamp features a lever that adjusts the ball joint rigidity, which in turn allows you to adjust the positioning of the arm system.