RAM Mount X-Grip Large Phone Mount with Drill-Down Base [RAM-B-138-UN10]X Grip Large Phone Mount with Drill Down Base The RAP B 138 UN10U consists of a 2. 5" diameter round base with the universal AMPS hole pattern, double socket arm and universal spring loaded X Grip cradle for cell phones. Designed into the mount is a 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