ProRadian Radian Scale Protractors: Learning Set of 2 Set of 2 protractors for learning about radian measure ProRadian 1 is scaled in 0.1 radians and ProRadian 2 is scaled in pi/24 radians Includes a mini lesson, find other lessons on proradian.net Sturdy, non-breakable laser-etched clear plastic Designed by a high school math teacher and curriculum specialist