Features a B-sized 1" rubber ball base that accommodates various size bars, depending on the model you choose. Fits 3/4" - 1" bars Sizing inserts are included to provide a snug fit and offer additional protection for the rail The mount utilizes nylon-insert locknuts to prevent loosening in high-vibration environments The included X-Grip cradle has a clean and clever four leg design that sports great holding power without hiding your phone behind foam pads and plastic The spring loaded cradle expands and contracts, allowing for a perfect custom fit to your cell phone Includes a device tether recommended for outdoor applications