Made of transparent plastic which permits observation of a joint's axis of motion and its range of motion. Assists in physical therapy by determining range of motion of a joint as well as evaluating and gauging recovery after surgery or physical therapy. The 360° head has three scales calibrated to be used with the International Standards of Measurement system – with 1° increments.. Each arm is 12 inches long and has a linear scale in both inches and centimeters.. The arms will also remain at the last measurement position until reset..