Ritchie B-51W Explorer Compass - Bracket Mount - White [B-51W] Entertainment | Accessories They are usually used for

They are usually used for small antennas

To make sure you get the  proportions right

Status indicators quickly convey information about antenna function and power

Its lockout feature prevents user from pressing down on opposite directions at the same time

Ritchie B-51W Explorer Compass - Bracket Mount - White [B-51W] Entertainment | Accessories They are usually used forExplorer Compass Features: 2 3 4 (70 mm) Easy to Read Direct Reading Dial Adjustable and Removable with Bracket and Thumbscrews Internal Green Night Illumination Built in Compensators to Easily Adjust for Deviation Scientifically Matched Sapphire Jewel & Hardened Steel Pivot Dial Movement Powerful DirectiveForce Magnets for Fast Heading Lock on Movable Sun Shield High Temperature Composite Construction for Extended Operating Range 100% Repairable