This is a probe designed to be used after pilot hole, get a feel for the walls of the osteotomy, poke to figure out if you have perf'ed anywhere. and overall just to give u quick measure on how far you need to go before widening your osteotomy hole. 
 
I use this probe after my pilot always to get a feel for the type of bone I'm dealing with and just to be safe to not drill too far and inadvertantly get inside sinus or impinge on nerve.
hope this helps