1-inch ball head, compatible with 1-inch phone holders such as RAM and GoPro holders. It could be clipped on the 0.67"-1.57" of rod / stick / handle / grip / pole / tube / hooks / shelves / plate / gun / desk / chair / tripod / railing / photo studio indoor & outdoor etc. Flexible fixed knob for easy tightening. ABS material, made of thickened material, will not break. 1" Ball Adapter for Handlebar Clamp Mount Base , Compatible with RAM Mounts B Size Double Socket Arm & Bike Motorcycle Phone Mount Holder