The RAM-B-138-GA40 consists of a double socket arm, 2.5″ diameter round base with the universal AMPS hole pattern, diamond adapter base and custom high strength composite cradle for the Garmin GPSMAP 78 series. Designed into the mount is a 1″ diameter patented rubber ball and socket system with adjustment points at the base and cradle. With a twist of the arm knob, you can move the flat surface GPSMAP mount to your optimum viewing position.