We've paired a B-sized 1" rubber ball base that accommodates bars 3/4" - 1" in diameter with the dynamic X-Grip. 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. This low-profile mount is the perfect way to secure your personal electronics and small accessories in any high-vibration environment. 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 X-Grip cradle expands and contracts, allowing for a perfect custom fit of your cell phone. The perfect complement to the modern sleek interior of today's vehicles, the RAM X-Grip is the cell phone cradle evolved. The X-Grip includes a device tether recommended for outdoor applications. The cradle is compatible with handheld devices that will fit the dimensions listed below. It is important to verify the dimensions of your handheld device with a case/sleeve/skin when determining the overall size.