I did a bunch of penetration tests a few years ago and the Zwickey Eskimo was one of the best heads, right behind the Grizzly. One of the hunters I guided, used the Eskimos and killed a very big buff, with one Grizzly to the heart. I didn't use them myself, since I needed much more point weight to balance my arrows and I think the Grizzly is a better head for the really big animals.