METRIC, 3/8” DRIVE, SURFACE DRIVE, STANDARD LENGTH, CHROME HAND SOCKET.  Surface drive sockets are designed to retain contact with flat sides of nut to transmit high torque and reduce nut wear.Compared to FLAT DRIVE, SURFACE DRIVE utilizes contact on the larger area closer to the center of the bolt or nut.SURFACE DRIVE 3/8 Sq. Dr. Socket 18mm Surface Length 32mm