This 180 protractor has an accurate ruler located at the base, plus a metric scale. Sharply defined graduated degrees are black and bonded in clear plastic. 4" ruler base. Box/12. Pack of 12. Clear protractor with sharply defined black markings. Accurate ruler located at base. Sets up and trues 30, 45, 60 and 90 degree angles. Plotting 0 to 180 degrees left to right and right to left.