Chrome Vanadium steel Total Drive sockets hardened & heat treated for strength with a fully polished mirror finish for resistance to corrosion. Can be used on a wide range of fasteners. All are suitable for Spline Metric Hex & Bi-Hex with many also equivalent to TRX-Star Whitworth Imperial Hex & Imperial Bi-Hex. Knurled ring for extra grip with greasy fingers. Supplied on rail.