The XTender HiRes 360°ISOM Goniometer measures the axis and range of motion of either large or small joints. The head can move 360 degrees and has three easy-to-read scales. The primary scale, which is found in the white ring of the head, reads in 1°increments. The stainless-steel arms screw into the goniometer easily and can extend from 12.5" to 33" for larger measurements.