Radian

You can use this model to explain the radian with your students. Radian is a unit of angular measure. It's defined as the angle subtended at the center of a circle by an arc whose length is equal to the radius of the circle. In simpler terms, if you take an arc whose length is the same as the radius of the circle, the angle formed at the center is 1 radian. 

6 radians with 1 circumference.  2π rad = 360°  and  1 radian= 57,296º.