Baseline Goniometer Plastic 12 Inch Arm Length The Baseline Plastic Goniometer is transparent device which permits observation of a joint s axis of motion and its range of motion. It 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 and is an essential tool for treatment rehab and surgical recovery. The goniometers arms are 12 inches long and have a linear scale in both inches and centimeters. 1 Goniometer 12 Inch Arm Length