The TENM120521 Bi-Hexagon, 12-point socket has the following specifications: Size: 21mm. Length: 38mm. Teng Tools specialises in a range of mechanics' hands tools to suit the price conscious professional user and the quality conscious DIY enthusiast. The Tools have been designed to Teng's own specifications, which meet or exceed British European or federal standards. This Teng Tools socket is a professional, bi-hexagon 1/2in Square Drive socket. It has been produced in accordance with ISO 9000 and AS954 specifications for increased torque and reduced risk of rounding fasteners. Made from chrome vanadium steel for strength and durability, with a satin finish.