The Ritchie Helmsman Flus Mount CombiDial Compass features exclusive built-in green NiteVu night illumination and compensators to easily adjust for deviation.• Type: CombiDamp Dia• Mounting Hole: 4 Inch• Dial: 3.75" Inch• Voltage: 12 Volt 3-3/4 Inch CombiDial x 6-3/16 Inch Overall Width 4 Inch Mounting Hole With H-741-C Protective Cover, HL-0219 Mounting Gasket, 45 Degree Lubber Lines, Built-In Compensators | Ritchie Helmsman Flush Mount CombiDial Compass, Black in Green