The Starrett A1 Arbor is designed for use with holesaws ranging from 14mm to 30mm. This high-quality arbor features a 6.35mm (1/4") high speed steel pilot drill and an 8.75mm (11/32") hex shank. Its sturdy construction makes it ideal for a variety of drilling applications. Brand: Starrett Suitable holesaw sizes: 14mm - 30mm (9/16" - 1.3/16") Pilot drill: 6.35mm (1/4") high speed steel Shank: 8.75mm (11/32") hex shank Screw thread: 1/2" - 20 Design feature: Set screw in the body allows for easy replacement of the pilot drill