Descirption: brand new and high quality Features: Ball for Head Diameter: 18mm, suitable for tablet/mobile phone holders that can be connected to 17mm/18mm bracket ball heads. Base Screw Hole Size: standard 1/4 or 6mm screw mount. Installation Position: can be installed above the screw for head of the tripod/selfie stick/camera holder. Applications: connect the mobile phone/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 ball for head, and then use 1/4"-20 mounting bolts to tighten the camera. Specification: Material: Nylon Length: Approx. 40 mm/1.57 inch Ball Diameter: Approx. 18 mm/0.71 inch Base Diameter: Approx. 21 mm/0.83 inch Base Screw Mount: Standard 1/4" Notes: Ballhead adapter only, other demo accessories are not included. Please allow 0-1cm error due to manual measurement. pls make sure you do not mind before you order. Due to the difference between different monitors, the picture may not reflect the actual color of the item. Thank you! Package Includes: 1 Piece Ballhead Adapter