3 colors of the thread restorer set : silver (UNC), black (UNF), and gold (metric), which is easy for you to distinguish . The thread chaser kit and each holes of the box are marked the specification, which can help you to find the right one you need quickly. The tool is made of high quality carbon steel ,the surface is oxidized,it is characterized by high strength, durability and corrosion resistance. The hexagonal thread tap and die can be used with any socket wrench. .
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