? This 17mm (0.67'') ball handlebar mounting base compatible with 17mm (0.67'') ball socket system. Not for 1 inch ball socket system. Works for Garmin GPS bracket & bike motorcycle phone mount holder with 17mm swivel ball mounting pattern. ? Main body made of 6061-T6 aluminum alloy for durability and reliability in the most demanding environments. CNC integral molding, solid structure. Anodized surface treatment, smooth surface, durable. TPU over-molded ball head, non-slip and wear-resistant. ? 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. ? 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). ? This 17mm (0.67'') ball handlebar clamp mount accommodates handlebars 0.5 inch (12mm) / 0.87 inch (22mm) / 1 inch (25.4mm) / 1.26 inch (32mm) in diameter. Tool-free design for easy installation or removal.