Navigator Compass. Navigator Compass Features: 4-1/2″ Ritchie CombiDial and Built-in Clinometer, Easily Installed, Fits 5.75″ (14.61cm) Mounting Hole, Internal Gimbal Systems for Maximum Stability During Adverse Pitch and Roll Conditions, Scientifically Matched Sapphire Jewel and Hardened Steel Pivot Dial Movement, Fiberglass Reinforced Bowl, 45 degree Lubber Lines, Exclusive Built-in 12V Amber LED Lighting, Built-in Compensators to Easily Adjust for Deviation, 100% Repairable,