The Milwaukee retractable starter bit provides accurate centering in less time when cutting tile, stone and glass. You'll cut clean, accurate holes faster when you use the retractable starter bit with Diamond Plus threaded hole saws. Diamond Plus hole saws deliver the best-in-class performance and the lowest cost per hole on the market with up to 10X longer life. With the highly durable retractable starter bit, N pilot holes are required. Its 1/4 in. size fits standard hole saw arbors. Use it with Diamond Plus threaded hole saws to increase your productivity when cutting hard, abrasive materials.