After losing two well hit birds last spring, I was advised to try these by the local bowhunting guru. Worked like a champ. I put them in between a 75 gr. Muzzy and the arrow shaft and, out of a 60 lb. bow, thehead penetrated about 2/3 of the way through the bird. I was shooting for the middle of the body. Bird couldn't fly or run with that arrow stuck in him. Was very difficult to get out. Had to stand on the bird and pull with both hands.