Hougen 14228 Holcutter-7/8 Diameter Quad-Lead uses a single arbor, with a patented Quad-Lead thread mounting system and pilot. The Holcutters, are not hole saws. Theyre precision ground, heat treated tools that easily cut thru the stock rather than ripping, tearing, and pushing thru as do typical hole saws. They can produce holes three times faster and cleaner than bi-metal 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 or twist drills. Holcutters now feature the patented Quad-Lead Thread System for faster cutter changes. Four individual threads on the arbor allows the cutter to quickly be threaded on or off the arbor. Arbor is for use in 3/8-inch or larger drill chucks.