The steel after heat treatment has high hardness and black oxide coating on the surface to prevent rust. It is durable and will not become dull after hundreds of times of use. Size:216 x 11 mm (8.50 x 0.43 inches), There are 8 different metric thread files in one piece-0.75 / 1.0 / 1.25 / 1.5 / 1.75 / 2.0 / 2.5 / 3.0 mm. Thread Repair File was Designed to repair damaged external threads on studs, bolts, screws, pipes and fittings. Thread Repair File Handle 0nly suitable for external threads, not for internal threads.the handle can be turned over, the detachable rubber sleeve is easy to slip off, and it can be switched as needed. Suitable for left-hand or right-hand thread. The operation is simple, a few minutes of work can allow you to easily fix the thread and tighten the nut.