The RAP-B-138-GA46 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 Montana 600 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 Garmin Montana flat surface mount to your optimum viewing position. This mount is designed to hold the following devices: Garmin Montana 600 Garmin Montana 650 Garmin Montana 650t Material: High Strength Composite Ball Size: 1" Rubber Ball "B" Size Note:Part number reflects product packaged in clear clam shell for store shelf display.