Explorer Compass , Explorer Compass Features: 2-3/4″ Easy to Read Direct Reading Dial, Viewing is adjustable to 30 Degrees, 12V Night Illumination, Built-in Compensators to Easily Adjust for Deviation, Easily Installed, Fits 3″ (7.62cm) Mounting Hole , Scientifically Matched Sapphire Jewel & Hardened Steel Pivot Dial Movement, Powerful DirectiveForce Magnets for Fast Heading Lock-on, High Temperature Composite Construction for Extended Operating Range, 100% Repairable,