TERRIBLE and I love to write a lot of five star reviews. This is one of two cobalt drill bits from Bosch that broke trying to drill through hardened steel in about 1 minute. And I got on the phone with a Bosch rep about how this type of drill is best for hardened steel (something that was difficult to drill). It's actually spring steel like that found on many pistol holsters, extremely strong BUT I've never had a bit break completely in two, ESPECIALLY two bits and under a minute! And I have drilled many holes in such steel. I should also mention that I use proper technique, with oil or water, not too fast. And I should add, Amazon has contacted Bosch regarding this and I have received NO response. . I'd probably name them myself, but both this bit and the other BOTH break so easily I'm done with Bosch (sorry!).