?The package comes with three rubber ring inserts to provide a snug fit and protection of the mounting surface. Three rubber rings diameter are: 0.5'' / 0.87'' / 1''. It fits to most bike,motorcycle,ATV handlebar rails. ? 0.67" ball mount base handlebar mount compatible with RAM Mounts and socket arm component, such as navigation mounts, action camera mounts, bike & motorcycle phone mount holders and others electronic device holders. Suitable for bike, bicycle, motorcycle, stroller, mountain bike, dirt bike, road bike, golf cart, electric scooter, ATV, etc. ? the mounting ball made of high quality aluminum alloy.It is durable and reliable in the most demanding environments. The ball joint adopts CNC-molding design, with anti-slip performance.0.67" 17mm ball mount holder fits for handlebars from 0.5" to 1.26" in diameter. ?this ball mount base utilizes rubber-insert and lockbolts to prevent loosening in high vibration for mounting to motorcycle,ATV or bike handlebars as well as other round rails within the insturcted dimensions. ?With this 0.67"(17mm) ball adapter mounting kit, you can 360°rotate your Gamin GPS, camera mount or bike phone holder device , it is suitable for outdoor riding and photo shooting.Small shape and compact size, the handlebar clamp mount base is easy and convenient for us to take and carry. This bike phone mount holder is tool-free installation.