A special round head protractor made by Shinwa. It is an excellent tool for reading angles & for scribing. It is made of stainless steel construction with a satin chrome finish on the round head. The graduations on the rule blade are metric, with mm increments & are etched in the steel. The knurled knob tightens the blade at any angle on the protractor & the scale on the round head reads up to 180°., Shinwa No. 19 Protractor ~ Stainless Steel