IRWIN® Impact Performance Series sockets have six-point deep wells with recessed corners that drive torque across the flats, for a secure fit and long life. They're manufactured with heavy-duty chrome molybdenum steel for maximum durability and long life with impact tools, and their thin wall construction allows for easy access in tight spaces. They have a black oxide finish that resists corrosion and increases the life of the socket, and the socket size is clearly identified with large, permanent, laser-etched markings. The 3/8" square drive enables use with impact wrenches, and the extractors are also compatible with 1/4" impact drivers when used with an adapter. If 1/2" drive size: The 1/2" square drive enables use with impact wrenches, and the extractors are also compatible with 1/4" impact drivers when used with an adapter.