This is a "D" sized (2.25") ball mount for marine electronics. It consists of a short double socket arm, a 3.68" diameter round base and 11" x 3" (27.94cm x 7.62cm) rectangular base.

The round base contains pre-drilled holes, including two holes at 180 degrees and three holes at 120 degrees, and 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.

Plate Hole Patterns (PDF)

Compatible Devices:
Garmin Fishfinders and GPS Chartplotters 
Humminbird Fishfinders and GPS Chartplotters 
Lowrance Fishfinders and GPS Chartplotters 
Raymarine Fishfinders and GPS Chartplotters

• Overall Length: 8.125" (20.63cm)
• Weight Capacity: up to 6.8kg
• Material: Powder Coated Marine Grade Aluminium
• Ball Size: 2.25" Rubber "D" Ball Size

Note: The "U" in the part number reflects product packaged in poly bag. 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.