Combination sets are useful for all types of mechanical jobs. The set is comprised of a straight rule protractor, a square head, and a center head. The protractor is graduated to read from zero to 180o in both directions. The rule is made of stainless steel and is graduated in both 0.5 mm and 1 mm increments. The square head has a level and a scriber point. The protractor head, center head, and square head are all made of cast iron.