Wow these drills cut very well and saved me. Well I had to wait two days for them to arrive but it was worth it. I needed to enlarge 6 holes in a very hard porcelain tile and was able to do it with just one of these diamond drill bits. This drill still has cutting ability, so I may use it in the future. Used water for treatment and everything went incredibly well and quickly. Just buy them and don't worry that they are not well-known brands or that they are too cheap. They work. Note, however, that they are slightly smaller than their advertised counterparts. More specifically, I have 8mm, which should be 5/16 inch. But they are a bit smaller than that. In my case, however, 8mm was the perfect size, phew!