WHO KNEW? not me. No one ever told me that there was such a thing as a pilot drill bit. In fact, when my old bit was getting dull and I bought a new one to drill through my RR Plates I bought the one on the right without even knowing it was different. Notice the bit on the right sticks out more in the middle. It has changed my life! I used to have to put in a small bit to make a start hole in the plate, constantly switching bits to get the holes drilled, some of the RR Plates are ungodly thick and seemingly undrillable. Now I use one bit and it goes through like a knife in warm butter.