Blue Boar Heavy Duty 7/16-inch shank Quick Change Dual Arbor Mandrel Kit for Hole Saws from 5/8&rdquo; to 7&rdquo; diameter, with both 5/8&rdquo;-18 and 1/2&rdquo;-20 thread mounts. Use 5/8-18 2-pin mount for hole saws 1-1/4 and larger -20 adapter for smaller saw 7/16-inch hex shank for greater gripping capability in the chuck. Use with standard arbor extension Comes with standard 1/4" by 2" high speed steel pilot drill bit Dual Arbor Kit provides Two Hole Saw arbor mandrels that store in the space of one ordinary arbor