This Milwaukee Hole Saw Arbor has a 1/4 inch shank with 3 milled flats for greater gripping capability in the chuck. It can be used in 1/4 inch capacity drills and larger. The arbor has a 1/2-20 thread and can be used on hole saws from 9/16 inch diameter through 1-3/16 inch diameter. It can be used with 49-56-8003 pilot bit which is supplied with this Arbor. One arbor and pilot bit per package.