The STEELMAN PRO 99044 10-Piece Swivel Head 3/8-Inch Drive, 9-Inch SAE Impact Extension Socket Set was designed to get into hard-to-reach spaces where maximum power is needed. This set includes 10 swivel-tip extensions 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. Each socket can pivot up to 30 degrees, providing a high degree of flexibility and allowing for a wide range of applications. The SAE sizes included in the set are: 5/16, 3/8, 7/16, 1/2, 9/16, 5/8, 11/16, 3/4, 13/16, and 7/8-inch.