W&P 142 0.14 inch thickness, solid brass arms and handles. Wt. 7 oz. These navigator's parallel rulers are inscribed with full 180º protractor markings. The middle of the bottom edge forms the protractor center when the arms are closed. This tool combines the essential features of a protractor plotter and a basic parallel ruler. Allows courses to be measured from a convenient meridian. Made of extra strong, crystal clear acrylic.