Alloy steel, more durable and rustproof.Various specifications, fit a variety of screws.Supply a steel socket retaining rail, easy to storage.Increase the torque angle, special arc angle design, the operation does not slip, more security.Surface plating chromium treatment, corrosion resistance is strong, not easy to rust, prolong the service life of the sleeve.Widely used in ng, metallurgy, shipbuilding, auto repair and other industries, mechanical maintenance and screw assembly and disassembly.