I use these with a Milwaukee hand drill and so far they have worked very well. I've mostly used them on concrete/brick which required a lot of force for me to drill a hole and so far I've used them quite a bit. And so far none of them have broken so I think that shows they are very good and strong! However, I don't know if the head wasn't that sharp to begin with (maybe that's why it was difficult to drill into concrete/brick) or if my attempts to drill it dulled the heads, but then I had trouble getting the to start drilling on some wooden boards. So they can be sharper or stay sharper longer (for my use) but at least they're durable!