The Starrett A1 arbor and A2 quick hitch arbor both have hexagon shanks and 6.35mm (1/4'') high speed steel (HSS) pilot drills. The quick hitch mechanism allows hole saws to be changed quickly without the use of tools. The pilot drills can easily be replaced by releasing the grub screw in the body of the arbor.
Sizes A1 Arbor 8.75mm (11/32'') Hex Shank - use with 14mm - 30mm hole saws. A2 Arbor 11mm (7/16'') Hex Shank - use with 32mm - 210mm hole saws.