I have used Thunderheads for years with much success. Many pass thrus and a few poor shots (hunter error) that still wound up as venision in the freezer. I once hit a doe (100 lb dressed weight) though both shoulders. The arrow did not pass completely through, but would up with about 6" of shaft sticking out of the exit side. There was only 1 blade slightly bent. I have never had any problems with the O-ring either. So, IMHO, you can' t go wrong with them.