Having seen other reviews I bought a large pack thinking they would only do a few holes drill . So far I've only used 2 drill bits to drill over 40 holes. I use them to make pots for succulents and violets from cups, serving bowls and other found objects in a variety of materials. I use a small bench drill, a small amount of cooling water and medium pressure. Release the drill a few times to allow the water to clear and the bits to cool.