The STEELMAN PRO 99046 5/16-Inch Swivel Head 3/8-Inch Drive, 9-Inch Impact Extension Socket was designed to get into hard-to-reach spaces where maximum power is needed. This SAE extension socket is made of high strength, heat treated 4140 chromoly steel with a black oxide finish. The knurled shaft allows for easy hand-starting and tightening of fasteners to prevent cross-threading. The pinless joint design transfers more useable torque to fasteners than a universal joint design, and also provides safety from flying projectiles that such designs can create upon failure. The socket head can pivot up to 30 degrees, providing a high degree of flexibility and allowing for a wide range of applications.