Reverse pilot bits are designed to bore out the inside diameter of pre-shaped cork grips 12-13" in length with a minimum ID of 9/32". The bottom edges of these concept bits have been ground to become the cutting edges and the pilot will be tape arbors wound onto the shank of the bit below the cutting edges. Enlarging the ID is done by pulling the bit half way through, and then reversing the bit, and finish boring by pulling the bit through from the other end. The boring meets in the middle of the grip and prevents chipping and ragged edges from the bit exiting the grip. The bit is not pushed through the grip. Available in 4 sizes.