Optional Tether Included The RAP-HOL-UN7B-354-TRA1 consists of a Track Ball base, composite double socket arm and universal spring-loaded X-Grip cradle for cell phones. This design features a 1″ diameter rubber ball and socket system with adjustment points at both ends of the socket arm. The spring-loaded X-Grip cradle expands and contracts, allowing for a seamless fit with your phone. The kit is the perfect complement to the modern and sleek interiors of today’s vehicles, and is compatible with virtually any track system including the RAM Tough-Track. 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. Cradle Dimensions Minimum Width = 1.875″ (Minimum Height = 4.25″) Maximum Width = 3.25″ (Minimum Height = 2.25″) Depth = 0.875″