The RAP-111U consists of a 2″ x 1.7″ 2″ x 1.7″ square base that contains the universal AMPs hole pattern, STANDARD LENGTH double socket arm and 6.25″ x 2″ rectangle base. 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 RAP-111U is Compatible With:Garmin Fishfinders and GPS ChartplottersHumminbird Fishfinders and GPS ChartplottersLowrance Fishfinders and GPS ChartplottersRaymarine Fishfinders and GPS Chartplotters Material: High Strength Composite Ball Size: 1.5″ Rubber Ball Size