RAM MOUNTS' RAP-B-138-UN7U consists of a 2.5 in diameter round base with the universal AMPS hole pattern, double socket arm and universal spring-loaded X-Grip(R) holder for cell phones. Designed into the mount is a 1 in diameter patented rubber ball and socket system with adjustment points at the both ends of the socket arm; this with a twist of the arm knob, allows you can move the mount to your optimum viewing position. The included X-Grip(R) 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(R) holder expands and contracts, allowing for a perfect custom fit of your cell phone. The perfect compliment to the modern sleek interior of today’s vehicles, the RAM X-Grip(R) is the cell phone holder evolved. Material: marine grade stainless steel components and high strength composite ball size: 1 in rubber ball "B" size.