Made of heavy duty industrial grade tungsten steel for high strength and durability These tools are mainly useful for creating threads on steel, stainless steel or other soft materials The 40 Pieces Metric Taps and Dies all come together in a molded storage box Ideal for re-threading fasteners and fixing holes, for auto and mechanical repair. Perfect set for the professional and amateur craftsman. Known for their ability to be used easily, these Taps and Dies are the most commonly used style and are perfect for most hand threading applications.