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.