Description: This 17mm (0.67'') ball handlebar mount accommodates handlebars 0.5 inch (12mm) / 0.87 inch (22mm) / 1 inch (25.4mm) / 1.26 inch (32mm) in diameter. Package come with three soft rubber ring inserts to provide a snug fit and protection of the mounting surface. Rubber ring inserts diameter: 0.5''(12mm), 0.87''(22mm), 1''(25.4mm). You can add or remove rubber ring according to the diameter of handlebar. When the rubber ring insert is not embedded, the hole diameter of the handlebar mounting base is 1.26" (32mm). The handlebar ball mount utilizes rubber-insert and lock-bolt to prevent loosening in high vibration for mounting to motorcycle & bike handlebars and rear-view mirror as well as other round rails within the stated dimensions. An Allen key is included with the package to facilitate your installation.Package includes:1* 1'' ball base.3* Rubber ring inserts.