They are very thin and they work but you need to know how to use them. You need to keep them cool and moist. I use a spray gun and run the drill with one hand and constantly spray the drill/hole. do not push too hard and do not perform the exercise too quickly. Be patient. Especially with porcelain stoneware. I bought them to install handrails in a porcelain stoneware shower. Drilled 10 holes and used 6 bits. I used to buy a $20 bit that ran out after about 10-15 holes. such a cheaper option and all the reason to pack them by the dozen