Stanley Proto JSCVM12 Reverse Ratcheting Combination Spline Wrench, 12mm Special heat-treated alloy steel permits slim shanks for strength and durability. Box ends incorporate the TorquePlus system Ideal for use on stubborn or damaged fasteners helps to extend fastener life, and allows the user to more easily turn worn, rounded, or rusted fasteners. Corrosion resistant and easy to clean surfaces.