Our extensions feature the largest knurling surface, offering the most control. The knurling on the female drive end helps when hand-tightening or working with oily materials. Additionally, select extensions have knurling on the shaft for more control. Chrome plating offers corrosion and rust protection. All Milwaukee Mechanics Hand Tools are backed by a lifetime assure.Largest knurling surface – precision controlKnurling on female end helps when hand tighteningCorrosion-resistantRust protectionEasy-to-read size identification