Helmsman Compass: 3-3/4" PowerDamp Flat Dial, Easily Installed, Fits 4" (10.16cm) Mounting Hole. (NOTE: Be sure you print the template Actual size), Exclusive Built-in Green NiteVu Night Illumination, Built-in Compensators to Easily Adjust for Deviation, Scientifically Matched Sapphire Jewel and Hardened Steel Pivot Dial Movement. Powerful DirectiveForce Magnets for Fast Heading Lock-on, Movable Sun Shield, 45 Degree Lubber Lines. High Temperature Composite Construction for Extended Operating Range, Adapter Rings Available. Sold separately. 6" (15.24). Retrofits Existing Mounting Hole for Model No. HF-72 order H-ABLK. For Model No. HF-72W order H-AWHT, 100% Repairable.