Stainless steel spring. The short leg is secured between two layers of Orfit Classic. The long leg is bent to size. At total finger flexion the spring is tightened up to a torque force of ca. 2000 g.cm. The spring is especially designed for finer extension assists in combination with the Orfit Splint. Gauge 1mm (1/24") - coil diameter 4mm (1/6").