4", Bi-Metal, High Speed Steel, Hole Saw, With Rapid Core Eject, Push Button On The Blade's Integrated Arbor To Move The Hole Saw On Or Off The Pilot Drill, Push Button Again & Slide Back The Adapter To Take Out The Plug, Cut Holes At An Angle & Easily Enlarge Existing Holes, Uses Hex 10 Arbor Diameter, Hang Tag.