3 pack of 21mm 1/2" Mid-Size Impact Sockets, & Pin & O-Rings, compatible with the Kielder KWT-002CS 1/2” Impact Wrench, as well as other brands that feature similar friction-ring style square drive. Pin & O-Ring is designed to lock the socket on to the square drive of the Impact Wrench, for essential security when working on site & at heights. The socket is only 52mm in length making tight spaces more accessible, when attached to the impact wrench.