RE: Thunderheads....?
I shoot the 100 grain pro series Thunderheads and have had nothing but excellent results with them. I have not had a problem with the rubber o-ring when shooting carbons either. The metal UBAR rings came with the pro series heads when I bought them last year but I could not get my arrows to spin right when the rings were installed. I just left them off and shot my arrows and broadheads the same way I have for the past several years.