This nut bolt extractor socket set is made of superior 40CR material, with high hardness and durable in use. These tools can be driven with a metric wrench or socket for quick work. Suitable for 9, 10, 11, 12, 13, 14, 15, 16, 17 and 19 mm heads. Spiral cut teeth provide a positive grip for removing rounded or damaged bolts. This is a set of 11 heavy duty tools to help remove nuts, bolts, screw heads, studs etc. .