3/8in. Drive, Bi-Hexagon Socket, 5/16in. A/F, Whitworth, 12 Point

Bi-Hexagon Sockets
12 point – side drive design gives a higher torque than normal sockets, grip worn nuts and will not round off existing nuts. All have a ball-retaining groove on each face of the square drive, which ensures a positive fit with accessories. Require only a one-twelfth turn to engage the next point of the socket.