I had to drill a hardened bolt out of a gap with a small gap. With cutting oil, I started with the second smallest drill bit and worked my way up: very sharp, impressive. However, I switched to the biggest piece to finish it and it crashed immediately on the first pull of the trigger, very glad I was wearing goggles. Very obvious manufacturing defect. I've never seen a drill break so quickly. The other bits were hard and sharp enough that I was finally able to dig out enough steel to break the bolt. Advantages: Very good hard and sharp drills. destroyed immediately upon first contact with metal. The holes in the plastic bracket were too big and 3 bits just fell out. Fixed with a heat gun to be usable. Conclusion: The non-defective bits were so good that I bought another set. Hopefully most will stop this time.