3/8”Anti-rotation adapter is compatible with the following friction arms: 244Mini Friction Arm, 244 Micro Friction Arm, 244 Micro Friction Arm with Anti-rotation. The adapter can be replaced using the included hex key. The Anti-rotation system is compatible with Manfrotto products: 055 series, 190 series, and 386B-1 Nan Clamp. Technical Specifications: attachment (top) 3/8'' attachment type material aluminum weight 0.08 lbs.