The RAM-D-111-C consists of a 3.68″ diameter round base, SHORT double socket arm and 11″ x 3″ rectangular base. The round base contains pre-drilled holes, including two holes at 180 degrees and three holes at 120 degrees. The rectangle base contains different combinations of pre-drilled holes which will match up to many electronic devices and mounts, including Marine GPS, CB Radios, Ham Radios, Gimbal Brackets and more. The RAM-D-111-C is Compatible With: Garmin Fishfinders and GPS Chartplotters Humminbird Fishfinders and GPS Chartplotters Lowrance Fishfinders and GPS Chartplotters Raymarine Fishfinders and GPS Chartplotters Overall Height: 8.125″ Weight Capacity: Up to 15 lbs. Weight: 3.45 lbs. Material: Powder Coated Marine Grade Aluminum Ball Size: 2.25″ Rubber „D” Ball Size Note: Part number reflects product packaged in clear clam shell for store shelf display. The 11″ x 3″ rectangle base is a universal mounting bracket with a selection of mounting hole locations. In certain applications additional holes may need to be drilled for proper fit with your electronic device. Recommendations: For an extra tight grip, RAM recommends the RAM-KNOB9HU handle wrench. The RAM handle wrench is designed to be used with the knob found on „D” size ball arms and mounts. The wrench matches the shape of the knob found on the side of „D” arms, and lets you give the arm an extra tight grip. This wrench was originally made for the military when using the RAM mounts in cold weather, and the knob could not be tightened by hand.