Spline fasteners help tighten high strength bolts which are used in high torque load applications. * Spline helps reduce foreign object debris (FOD) by having a precise fit between the fastening tool and its fastener. * Black chrome finish is corrosion resistant and visually distinctive. * Ratcheting spline box end is countersunk for easy application to the fastener. * The fractional spline wrenches can be used on fractional 4, 6, 12 point and spline fasteners.