Protractor features a 6" open center and sharply defined graduations. Made of plastic. Protractor includes a 6" ruler.Editorial ReviewBlack-scored, molded-in graduations.Metric and standard measurement systems.Open-center plastic protractor perfectly fits the needs of young mathematicians. Black-scored graduations molded into the transparent frame ensure crystal-clear measuring. Ruler base lists both metric (10 centimeters) and standard (6 inches) systems. Degree Graduations: 1°; Material(s): Plastic; Ruler Size: 6" Ruler Edge; Color(s): Clear.