Troxell 21-BB14 Diamond Bullet Drill Bits 1/4"This bullet bit is a departure from the conventional masonry drill bit, in which it is a hollow design. The cutting surface is coated with industrial diamonds, and can be used wet or dry. (It is always recommended to use water when possible to extend the life of your diamond products) The main benefit of the bit is accuracy in hole placement, and providing a cleaner edge free of chips or burrs. Other sizes availableFeatures:Brazed DiamondsHollow designAccurate hole drillingNo drifting.