Proto® torque adapters are designed with a center-to-center dimension of 2 in. This means that the distance from the center of the square drive of the mating torque wrench to the center of the fasteners is exactly 2 in. This constant dimension serves to simplify the process of calculating the torque applied. Proto® Torque Adapter, Imperial Wrench Opening Type, 3/8 in Drive, 13/16 in Wrench Opening, 2-63/64 in Overall Length, 12 Points, Alloy Steel, Full Polished