6-point hex socket for maximum torque transfer to the face of the fastener. Precision cold-forged, hardened and tempered chrome vanadium steel. Fully polished and nickel chrome-plated for durable corrosion resistance. Chamfered ends and thin walls for positive location on fastener. Contents: 6, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 19 and 21mm.