This cutter comes with a small center drill shank that is spring loaded for easy stock removal. The shank uses a short 7/16" drill held in place with a 2.5mm hex nut. The spring is very stiff, so you have to use extra force when drilling. The medium shank is thread compatible with my set of Blu-Mol bits and even has locking holes so I can use a larger Blu-Mol shank with locking pins to keep the bit from loosening. The cutter is fine if you're careful, but it's nice when the cutter snaps into place when you're drilling holes in walls! The cutter falls into the wall. I got this hole cutter to make holes for some small electrical round boxes but ended up not needing it. I think $12 is a good price for a larger hole saw blade that will work with my other kit and even comes with a bonus shank.