Centering Pilot Bit with 5/8"-11 Male to 1/2" Shank Adapter for 9" Long Dry Core Bits Industrial grade heat treated steel centering bits fordry core bits.Giving you a more precise guide to your core drilling. Used for dry core bits with 9.5" drilling depth and 5/8"-11 Arbor Fits Drills with 1/2" Shank Arbor