Apex square drive sockets for spline fasteners. Spline sockets on spline fasteners help deliver twice the torque of 12 point wrenches on double hex fasteners, helping tighten high strength bolts to high torque loads. Spline helps reduce foreign object debris (FOD) by forcing a precise fit between the fastening tool and the fastener. Apex impact sockets are specifically designed and manufactured for high impact use, and made from a tougher and more ductile alloy steel which is then heat treated for extra durability.