Panavise 851-00 Knuckle Adjustable Knob and Screw (Black) Shaft screws into the adjusting knuckle. For an ultra low-profile mount, screw directly to one of our Mounting Bases! Quality manufactured and fully adjustable: 210-degrees Tilt, 360-degrees Turn & 360-degrees Rotation Knob and tamper-resistant set-screw adjusting options included Overall knuckle height approximately 2.5-Inch (63.5mm) 0.25-Inch 20 mounting stud with lockring