This 1/2" square 21mm Impact Socket is 80mm Long and includes a Retaining Pin/O-ring. It can be used for impact wrenches and racking automotive highways maintenance. The 21mm socket is commonly used with scaffolders. A steel pin is used to lock the socket onto the square drive of the Impact Wrench, and the rubber O-ring goes over the socket to hold the pin in place. It is ideal for scaffolders when working at height. It has high strength with a black oxide coating for prolonged life. It is fully compatible with all features and benefits, offering high strength for long life. The black oxide coating provides durability. Application: Impact wrenches, Racking, Automotive, Highways Maintenance. Features: Robust socket for impact wrench.