I use the NAP gobbler getter heads. NAP had them advertised a couple yrs back then they seemed to backoff, and haven't seen them in a catalog since. But I contacted NAP last spring, and they were still available. They are basically a spitfire mechanical, with larger blades, and a blunt tip. They are designed to slow penetration, and to hopefully keep the arrow in the bird to prevent fly away. I also drop my bow down in lbs to help with non pass through.