Hougen 13007C Holcutter 3 Pack Pilot Drill has a .187 diameter and is 1.88-inches long. This pilot is used with arbor 14009 for all Holcutters. The Holcutters, are not hole saws. Theyre precision ground, heat treated tools that easily cut through the stock rather than ripping, tearing, and pushing through as do typical hole saws. They can produce holes three times faster and cleaner than hole saws in sheet metal and have dramatically extend tool life, too. All sizes have a "shoulder" to prevent plunge-thru, which is especially useful when drilling into live electrical boxes. See for yourself why electricians, fabricators, and mechanics prefer the quality and speed of a Holcutter over hole saws. Pilots locate the holes center point and eject the slug at the end of the cut.