This is a set of 10 heavy-duty tools to help remove nuts, bolts, screw heads, studs, etc. It is suitable for 9, 10, 11, 12, 13, 14, 15, 16, 17 and 19mm heads. Spiral cut teeth provide a positive grip to remove rounded or damaged bolts. Made of hard alloy, they are very strong and durable. These tools can be driven with a metric wrench or socket for fast work.