The RAM-B-121-UN8U consists of a yoke clamp base, double socket arm system and universal spring loaded X-Grip cradle for 17.78cm (7") -20.32cm (8") tablets. The yoke clamp base will fit rails from 1.59cm (0.625") to a maximum of 3.18cm (1.25") . The 2.54cm (1") rubber ball is positioned at a right angle to the plane of the mount; when connected to a rail, the ball sits parallel to the rail. Designed into the mount is a 2.54cm (1") 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 spring loaded X-Grip cradle expands and contracts, allowing for a perfect custom fit of your 17.78cm (7") tablet. Included are extra easy access grip knobs, located on the back of the cradle for quick release of your tablet. 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.