✪ Head Diameter: 18mm, suitable for tablet holders that can be to 17mm/18mm bracket heads. ✪ Base Screw Hole Size: standard 1/4 or 6mm screw mount. ✪ Installation Position: can be installed the screw head of the tripod/selfie stick/camera holder. ✪ Applications: the tablet to the tripod bracket so that the direction can be adjusted 360 degrees. ✪ Easy to Use:Fix the adapter to any mount that fits the 17mm head, and then use 1/4”-20 mounting bolts to tighten the camera.