QEP 10572 .25" Porcelain Diamond Drill Bit with Drill Guide and Water Cooling System has a tough, diamond grit cutting edge for long lasting use, limited wear, faster cuts, less dust and less chipping. This hole saw must be used with the water system to keep it from overheating and must be used with a cordless drill. Convenient, single piece water delivery system keeps hole saw cool for a longer life.