I bought these for a plumbing project involving drilling porcelain stoneware and cement board in the bathroom. They worked well enough and cut a nice hole without too much trouble. The reason for the three stars is that although I was moving slowly and using a lot of water for the first three holes, the diamond wore out very quickly. Started a fourth hole in a hard to reach spot and the drill got stuck. It didn't break, it was bent badly, and I didn't try to pierce the incision with my muscles. Used the second bit to continue and finish the hole. It worked well, but again, the beat had pretty heavy gear. I knew I wasn't buying a quality racquet at this price. The best are much more expensive. I've bought them a few times and made a few. I will invest in a much better set in the near future. As said, you get what you pay for. If you only need to drill a few holes and don't want to spend a lot of money, then these bits will help you. If you're looking for something that will last through many projects, invest in either a good beat or a set of beats.