Made of ground stainless steel for optimum accuracy, the General Tools 17 Square Head Stainless Steel Angle Protractor delivers reliable measurements for students, machinists, carpenters, and woodworking hobbyists. This protractor features a 6-inch adjustable arm and is ideal for setting bevels, taking measurements, and transferring angles. The square head design makes it possible to securely anchor the protractor against objects as you take measurements. Deeply etched graduations read from 0 to 180 degrees in forward and reverse directions and will not wear or rub off. A knurled thumb nut allows the arm to be locked into position to quickly and easily identify angles. The stainless-steel construction glides smoothly and offers strength, durability, and resistance to rust.