6 * The plastic 360 degree scale ISOM goniometers have a head with 3 scales calibrated for use with the ISOM system * The clear plastic permits observation of the joints axis of motion and range of motion * 6 * The plastic 360 degree scale ISOM goniometers have a head with 3 scales calibrated for use with the ISOM system * The clear plastic permits observation of the joints axis of motion and range of motion *.