Stanley Proto J5100 3/8-Inch Drive Torque Adapter Set, 12 Point, 9-Piece Designed for easy torque calibrations Adapters measure 2-inch from the center of the square drive to the center of the adapter opening Special heat-treated alloy steel helps to increase strength and durability Box end wall thickness is specially engineered to provide strength while still allowing ample room for access to reach difficult fasteners 12 point box end allows for fine indexing, helping to improve speed and access. Fits 4, 6 and 12 point fasteners