Manufactured from hardened and tempered high grade Chrome Vanadium steel. Fully polished black chrome finish for resistance to corrosion. Feature specially machined flutes in the walls of the socket which enable use on up to 85% rounded fasteners. This not only provides added strength but also prevents damage to worn or rusted fixings. Contents: 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19mm. Includes knurled ring for extra grip with oily fingers. Supplied on socket rail. Power source type: hand powered