This Bogen/Manfrotto Hydrostatic Arm features a new locking mechanism. A ball pivot encapsulated in a hydraulic oil-filled chamber enables the arm to be locked in position with only a gentle turn of the knob. This is accomplished by the fact that the oil surrounds the ball joint and applies pressure evenly, as opposed to a traditional lock that simply jams a screw or cup against the ball.
The 819 Medium Hydrostatic Arm spans 7.1" (18 cm) and is a perfect bridge between a video camera and a small monitor under 4.9 lbs (2.2 kg) in weight. It also features both 3/8" and 1/4"-20 pins with standard tripod/camera threads.