The Arm Clamp Buoyancy from Beneath the Surface is used to hold in place a buoyancy arm on an underwater video lighting system. This clamp is a little longer and more heavy-duty than the Arm Clamp Standard / ACS. Like the ACS, the ACB is machined from an aluminum bar to a fine finish and then anodized to a rich black color for corrosion resistance in salt water. The hardware and spring are stainless steel. The clamp handle is an aluminum knob that is easily tightened.