From Manufacturer
Mounting this silver 1" Ball Arm from Beneath the Surface to a grip or base on your underwater camera tray enables the connection of a YS-style strobe or video light. At one end, the arm features a standard, black 1" ball mount for a clamp; at the other, it has a black YS connector for various strobes and lights from Sea & Sea, Olympus, Fantasea, and other brands. The arm is on the shorter side at 5" in length, which makes it useful for lighting close-up shots, but it can also be extended via the addition of another arm section and clamp.