After trying this Industrial and Scientific hole saw, I am thoroughly disappointed in its performance. The diamond coating was supposed to enhance durability and precision, yet it barely cut through the material I was working with. The price is not worth the quality of this product.
Not sure about the durability of these bits but for the price they are definitely worth it. Consider the price of just one of these bits at a large store. They worked great for drilling my ceramic tiles, don't forget to use a water bath for longer life. Would buy again.
I was trying to make a drainage hole in clay pots with a conventional drill and it broke after a few seconds. Using one of these (and plenty of water to keep the temperature down) I've made about 300 holes in clay and even ceramic pots. Works as it should. The first one is still going strong and has 5 more fresh beats in stock.