GN18 Features: -Round head protractor.-Material: Ground stainless steel for optimum accuracy.-Preferred by machinists, drafts people and mechanics for setting bevels, measuring and transferring angles.-Permanently etched graduations from 0 to 180 degrees in opposite directions.-6" Adjustable protractor arm locks into desired position with knurled thumb nut. Dimensions: -3.38" x 2" Head.