Hole saws typically have a pilot drill bit (arbor/mandrel) at their center to keep the saw teeth from walking.
MA-24 (1/4" Round Shank) fit for 9/16 - 1 3/16"
- M34 (3/8" Hex. Shank) fit for 9/16 - 1 3/16"
- M35 (3/8" Hex. Shank) fit for 1 1/4 - 6"
- M45P (7/16" Hex. Shank) fit for 1 1/4 - 6"
- MA45PS (7/16" Hex. Shank) fit for 1 1/4 - 6"