These bits surprised me. I bought them and they just sat there. Then I remembered when I had ceramic tiles that needed drilling. They worked like a charm. But they also go through concrete like water. Where my Bosch concrete drills can't get through with a hammerless drill, these drills go through concrete without a sweat. A piece of steel in concrete eats away the head of whoever I'm using and I'm a computer giving another command. YOU ARE REALLY GOOD