Very Useful: Diamond Grain provide fast and smooth drilling; Designed for drilling the faucet-mounting holes in counter tops and vanities, and to make clean rounded corners for square or rectangular sinkholes.Diamond Drill Bit integrated with wax lubricant inside which melts while dry drilling and cools the cutting surface; Water can be used as additional cooling to prolong the life of the bit6.0mm Drill. Great for drilling clean holes to hard materials especially tiles, porcelain ground, granite ceramic glass mirror marble stone masonry brick (not for wood)