Box end is countersunk for easy application to the fastener.
Fractional spline wrenches can be used on fractional 4, 6, 12 point, spline and Torx fasteners.
Spline design enables the wrench to contact conventional fasteners away from the corners, which applies force over a larger area, reducing risk of fastener scoring and helps prevent rounding of the corners and other fasteners damage that could lead to Fore
Spline design was created for use with specialty spline bolts which are used when weight and size of bolt heads must be minimized.
