Features: The combination of ruler and protractor, semicircular protractor at the top can measure from 10-170 degrees left to right and right to left. Protractor and ruler of angles measure tool are precisions etching, the readings are clear and accurate, easy to read, wear resistant and convenient for your use. Angles finder protractor crafted from carbon steel, with well durability and wear resistance, not easy to rusts, and can apply for long time, but notice that the peaked carbon steel border, please be cautious while using. Adjustable protractor arm: angles is quickly and easily identified by knurling thumb nut locking in the desired position, you can fix the angles to plot, suitable for setting bevels, draw radials lines, measuring and marking angles. Round head protractor is suitable for engineering, angles measurement, student drawing, architectural designs, carpentry, length measurement, gift for students, craftsmen, architects and designers. Specifications: Material:Carbon Steel Size:Approx.100mm/3.94''x150mm/5.91'',150mm/5.91''x300mm/11.81'' Package Includes: 1Piece Adjustable Protractor note: Please allow 1mm errors due to manual measurement. Due to the differences between different monitors, the picture may not reflect the actual color.