Socket head cap screws are ideal for applications in which there is not enough space to maneuver wrenches or sockets and have an internal-wrenching drive, such as a hex socket. Also known as socket head bolts. Black oxide has minimal corrosion resistance. Property class 12.9: tensile strength: 1,220 MPa or about 176,900 p.s.i. Head marking 10.9. Made from alloy steel, quenched and tempered.