Patented spiral flutes with one straight flute for sizing and finishing, The spiral flutes allow for the reamer to advance thru the boss with little external effort, also a tapered lead for easy entry. They only require a 7/16 Hex style ratchet wrench to use, No power tools needed!! The only reamer on the market that comes with 3 different undersize diameter pilots for an accurate finished hole. Also coming soon is the Reamer Extension! This will mount to all of our reamers and will allow you to ream out your spindle bushings straight thru. No more wrestling with this common problem, we are currently in the proto-type stage and there will be more details shortly.....stay tuned.