Dual Arm Equalizer Protractor &ndash; 18 Inch Anodized Aluminum Arms 18 inch arm lengths with a 4 inch diameter dial. Dial is graduated to the 1 degree with 1/2 degree readings possible. All parts are corrosion resistant and arms are made from Anodized Aluminum. Magnifying viewer improves ability for precision reading. Strong locking knob to fix an angle in place.